One thing that bothers me about Forums, not just ours, but others also, is that when a thread is started with a question, and that question, or questions, don’t get answered; it’s just like an Old Western, they “fade off into the Sunset”.
In order to answer the questions, and help straighten out the issue of the Rubber Plugs that John (the OP) inquired about, I believe that we need to get several things clarified.
NOTE : Due to the size of the Text and Attachments, this “clarification” will include Part I and Part II. I will Post Part II first in order that Part I can be read first.
Bob G :
a) In your Reply of June 3, you noted “…and it's square hole had the same plug installed from the engine side as other pictures posted.” The “other pictures posted” include John’s, Jeff’s and mine. In both John and Jeff’s pictures, there are 2 distinctly different rubber plugs shown. To which are you referring ? Both of their pictures, as well as mine, show the oval one that John was originally referring to; the other shown is a round plug in the square hole application ; pictures showing this show the round plug’s front and back, depending on whether it was inserted from the “engine side” or the “front of the car side”.
b) In your Reply of June 5, you noted that “…68's with original radiator supports will have the square hole which is actually made from the oval hole with oval top and bottom edge still evident and squared off sides”. Here you describe a modification (“made from”) to the oval hole, which I do not believe took place. All of the square holes with oval top and bottom edge that I have seen, have the axis of the oval top and bottom, vertical, so they couldn’t have been “…actually made from the oval hole.” I believe that a totally new die was used for the square hole, and not a modification of the existing oval hole, nor a modification of the oval hole die. A “modification” is considered an “altering of something existing to amend its form or shape”. I believe that the oval hole to square hole is considered more of a production change”.
c) In your Reply of June 6, you once again refer to the hole as a “modified square hole”. As noted above, I do not believe this to be the case. And yes, I have seen many of the square holes, and they are not modified oval holes (other than obviously “owner butchered ones).
You also note that the “oval plug”, of which you’ve seen many, fits easily into the square hole. Well, first, the “oval plug” that you describe and show a picture of, is not the “oval plug” in question. If you look at the dimensions furnished by John, you’ll see this. The “oval plug” you show also has a different Part # molded into it (376966-S) than the one in question (no, that’s not an 8 in the first digit, it is a “3”; there were no 6 digit Standard or Utility Part #’s that began with 8 in 1967). Finally, the “oval plug” you show in the picture is not an oval plug at all; it is a round plug that has been slightly distorted as the result of putting a round plug in a square hole.
d) In your June 7 Reply, you finally “change your tune” about the oval hole being modified, and note that “most likely” the die was modified. However, in looking at the oval stamped hole versus the square stamped hole, I don’t believe that this would have been feasible.
A closer look at the two different stampings shows that while they have parts that are similar (the overall length from “oval to oval” in particular), they are not identical. The oval, horizontal axis hole exhibits the rounded ends having a radius of 0.1695”, and thus a height of 0.339”. On the other hand, the square hole is 19/32” (0.59375”) on a side, with the top and bottom ovals having a radius of 0.15625”. While it would of course be possible to modify the horizontal axis oval hole die into a die for the square hole, IMHO, the cost to modify would probably exceed the cost of a new die (not to mention the fact that the horizontal oval hole die would be “lost”, prohibiting its use in other applications).
As far as my “left over inventory theory”, the only reason I interjected that was to give you some credence for your “modified hole theory”.
Here you again bring up the “oval plug” which you pictured, and as noted above, this is not the same oval plug in question, and also as noted, the one you pictured just appears oval. And, if you hadn’t noticed, the zoom feature works better than reading glasses or a magnifying glass.
Finally, while maybe not as many as you, nor definitely not as many documented as you, between car shows, swap meets, and junkyards, I have seen my share of Mustangs since 1976. Putting “real world” observations together with Ford documentation, makes a pretty powerful set of tools. Thus, my most obvious conclusion is that you haven’t dug deep enough into what you’ve seen on the surface.
To help slow down the “rabbit chase”, as Richard put it, I am going to summarize my take from the 4 pages of the “chase”
1) Early 1967 Mustangs had 4 oval holes stamped in the radiator support, their main axes being horizontal ; two on the right and two on the left, each pair located below and inboard of the front hood bumper support brackets. There is no apparent use for these holes on Mustangs. (Pictures 1 & 2)
2) For some reason, on Mustangs, the upper two holes received rubber plugs. On the early production Mustangs, these distinctly oval plugs had Part # 377841-S molded into them. Currently, there is no known source for these rubber plugs, other than from other 1967 “donor” Mustangs. (Pictures 3 & 4)
3) Sometime between the fourth week in February and the first week of March, 1967, the stamping of the horizontal oval holes was changed to a square hole stamping. The square hole stamping included a rounded portion on the top and bottom of the square. The reason for the square hole was to allow insertion of a captive nut (nut and retainer assembly) that was to be used for part of the headlight assembly for Cougars (the same radiator support was used for both Mustangs and Cougars). (Picture 5)
4) The rounded portion on the top and bottom of the square hole, was apparently to allow insertion of a round rubber button plug when this same radiator support was used on Mustangs.
5) Once again, the rubber plug was only used in the top two holes on Mustangs. These round rubber plugs had Part # 376966-S molded into them. These plugs can still be found both NOS as well as at your Ford Dealer. At the time of this Post, at least 15 Ford Dealers had these in stock; at others, they can be ordered. (Interestingly, this same button plug, Pictures 6 & 7, was used in the rear inner fender aprons, 3 on each side).
6) Based on observations by others, rubber plugs installed in the Radiator Support on Mustangs at the San Jose Plant were installed from the Engine Compartment toward the front of the car. Cars built at the Dearborn Plant appear to have had the plugs installed from the front toward the rear. While the sample size is small, cars built at the Metuchen Plant appear to have had the plugs installed the same as the Dearborn, from the front toward the rear.
While we haven’t really answered John’s original question as to a source (other than from donor ‘67’s) for the oval plug in question for the Radiator Support, this will hopefully help explain any confusion of the oval and square hole applications, as well as the rubber plugs used for them. (Pictures 8 & 9 - side by side Plug comparison).
As far as the “second part” to John’s original question, the rubber plugs for the inner frame rails near the idler arm and steering box mountings, this plug is Part # 378770-S. I am not aware if they are being reproduced, but they can be found NOS. (Picture 10)
Hopefully, this has provided at least some clarification and partial answers to John’s original questions.
