The subject of the type or style of fuel sender sire retainer on the drivers side of the trunk came up in a recent discussion and I thought I should share the information found here also
There were two different style of retainers used. The early that were like 1966 versions . .
I cannot find any reference to a 1966 Mustang (or 1965 either) trunk lamp.
There were two different style of retainers used. The early that were like 1966 versions and the later metal style ones. The change apparently took place around the end of Jan to possibly the second week of Feb 1967 based on data collected from unrestored Mustangs/Shelby's built at San Jose. Sorry don't have real build dates for the cars specifically around the change over period.
As a point, yeas there is a short section of strap metal in the base of the plastic S shaped version but its mostly just plastic so I often refer to them as the plastic and metal versions. The metal version was rubber dipped to protect and insulate it.
Hope this helps others.
The "early" version has a Ford hardware part number of 372303-S100 as shown in the "1967 Mustang Electrical Assembly Manual" (AM0019) pg61, item 3.
(Note: Reference the AMK Bulk Fasteners, 2019 ed, pg 134, they indicate that 372302-S* is "similar" to 372303-S* with the finish dash of -S99 equal to a -S8 (clear zinc) and rubber insulator, pictorially partial covered.)
The picture of the "Late" clip appears to be either Ford hardware part number 352375-S (not used on any 64-73 Mustang) or 372047-S**, which is a relatively common clip as a -S100, with a rubber coating over about 3/4 from the bend to over the "grip", available from AMK. There is no apparent rubber in the picture.
As to use dates, the above Electrical Assembly Manual is "vague", stating only that the drawing revision date of 7-22-66 "Revised (item-3) Reqmts" , but did not change the part number.
Jim