[Red80TA]

Most original rear spoiler parts that still feature dried sealant blobs on the studs will also include a small gold-anodised washer pressed in to it, or rather, under it. It appears the washer was always against the part and the sealing washer compressed over it.

Firebird rear spoiler 5-16 brass shim washers go against part by Ben, on Flickr

Firebird rear spoiler corners used set 493687 493688 (4) by Ben, on Flickr

Firebird rear spoiler corners used set 493687 493688 (4) by Ben, on Flickr

The sealing washer, basically a ring of formed putty was GM part #7583551 for these particular parts. There is never a reference to a separate washer added. I'm wondering if the sealing washer was attached to the back of the steel washer as a component. I have never seen a NOS #7583551 or similar to study. I the washer not only overlaps the area of the hole being sealed but also gives a nice flat and square face to the mount which may not be the case in every casting or component mounting up.

Other areas that appears to have these same small sealing washers were 74-78 rear light cages with the helmet nuts. Sometimes the sealing washer is attached to the nut, other time it appears to be added separately, with metal washer left pressed into it.

The larger rear bumper bar mounting studs to the body also used large sealing washers with the bright orange seal attached to the washers which then compress to form a ring. Not only were the seals on the inside of the trunk, there were also seals in between the bumper bracket and the rear body panel outside.

Firebird 74-78 rera bumper brackets with sealing washers at top (2) by Ben, on Flickr

Firebird rear bumper upper sealing washers used 463120 (3) by Ben, on Flickr

[Red80TA]

Standard response after I spend all day replying to other posts.

[Skip Fix]

I found some similar sized brass washers and used 3M strip caulk/putty.

[Red80TA]

Uhuh . Not brass.

[Red80TA]

No one interested yet everyone has them.