What the GM Heritage center will send you is the vehicle invoice sheet, which included pricing. The build sheet (akin to the mopar broadcast sheet) would not have pricing, just the options for the assembly line to put the correct parts on. The information otherwise would (should) be the same though.
like the mopars, the build/broadcast sheets were for internal routing and usage. So some may have them under the seat in the springs, some behind pillar trim, under the dash pad, etc, some may had been tossed and never left with the vehicle.
Not a squarebody of course, but my dart had 4 broadcast sheets in it, all belong to it and match, one around the steering column, under the front seat, under the rear seat, and under the carpet.
here’s a picture of a 67-72 truck build sheet, which would be similar to a square body. I have partial fragments of one from a 74 GMC
(photo courtesy of another forum)
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