[Shiny]

The fastener is indeed designed to spin freely and NOT clamp the strap.

I could not say if the straps I removed were original or aftermarket. The only marking I found was "W". There definitely was a clearance hole on the fastener entry side of the bend:



The start of threads on the bolt is ~0.7" from the flange. The strap is ~0.095" so there is about 1/2" of "thread-free", reduced-diameter bolt.

3 washers are thicker than the bracket on the car. When I started the bolt, it cleared the outer hole:



When tightened, the threads pulled through the strap and then "exited" the far end without fully clamping the strap. The bolt clearly "spun freely", effectively being a "self-stripping" fastener. The threads that were formed in the strap allowed the bolt to be removed easily:



Net:

- The strap is not clamped "by design"
- The special fastener makes it all happen
- The repro fasteners with full threads don't accomplish the assembly as intended by Pontiac

I'm not too worried about any of this, but as I said, I see this as a very clever system to assure the strap tension is held by the bend and not by the clamped connection. Why? Dunno.....

I can't read the part number for this fastener (#13 on the 1970 assembly drawing). It looks like 399782 ??? Anyone have a clear PN for this?

Mike