Will the Tonneau from a 91 firebird fit a 89 camaro?

Yes it will fit. The Firebird or Camaro issue is irrelevant. It will look a bit strange because there will be a hole where the shoulder straps should come thru above the seat and below the tonneau cover. You should get a 87-90 tonneau instead. You will also have the option of relocating your tonneau release switch to the new location just in front of the slide handle that releases the pin or just removing the plastic shroud that covers the switch in this new location and filling the hole with a piece of aluminum sprayed matte black.

Lon

Lon,
On my 89, I have considered converting over to the later style tonneau cover. I really do not like the shoulder straps attached to the cover itself, it is a real pain to buckle up in the back seat with the separate shoulder harness.

How hard would it be to take the pieces from a 91/92 with the shoulder harness attached to the floor and convert an 89?

If I may answer, John it's not difficult to do, you have to find the set up in a 91/92

I assume it would just bolt in?

If you're talking about the ones with the plastic pods around them...

BTW...Bill Speeds Formula convertible I have, when I got it off the truck from Minnesota, The GTA rims were switched fronts on rear and rears on front...and the front rim mounted on rear one was missing a chunk.

Sure you "just bolt it in" AFTER you weld the threaded plate in to attach it to. The sheet metal alone is not substantial enough to attach it to.

Lon

What are you referring to. Are you referring to the shoulder harness for the back seat?

I know that in 1989 GM added the back seat shoulder harnesses. Apparently ASC did not use the same mounting point?