I don't usually cross-post across forums, but I'm still looking.
I suspect his area of my car was dismantled at one time by others, so I don't want to use the parts I removed without validation.
I have the 67 Shelby Master Assy Manual but the information on the rear cap installation to body is sparse. Page 31 lists the components to assemble the rear end caps to the body, but there are many blanks and issues.
The '1.B' bolts [attachment bolts of cap to body] are listed as 378190-S2 which are not found in Jim's hardware list. This may be a misprint and may actually be 378196-S2. I have lots of the later as they are simply small tooth washer bolts, like those used on the trunk hinge.
There is a "Seal, Felt" listed that is supposed to go between the small tooth washer bolt and the body. It's listed as a 380002-S (washer with plastic washer), which AMK simply lists as a washer. Something amiss here with either AMK or it's a washer I've never seen.
I suspect SA may have just used black strip caulk around the washer/bolts since they used a metric ton of the stuff to seal the rear taillight area.
And then the three screws on the bottom tail of the cap which screw the tail to the body. These are badly displayed in the manual as a '1.D' (376362-s #6x1/2) screw, but that seems odd given where they go. Plus since they are bare I would think something better than S or even S2 as the caps are painted prior to installation and not on the car.
The car is going in for paint in the next few weeks ...