Wiring and computer interchange info source?

[ah.b.normal]

Looking for a info source for interchange and ID-ing Computers and wiring harnesses(from Cobalts). My pile of stuff is wide ranging and varied. Many bits came with failed repairs or projects with little or no info on where some of the bits came from.......... In my early research days I picked up castoff bits in various junk yards, fuse panels and pieces of wiring. I have 2 mystery BCM's, they have labels on them but the numbers tell me nothing so far. (Might as well be in Pre-Sumarian Cuneiform Hieroglyphics.) Several PCM's with no history, just numbers. GM had to have this info in order to repair these units! Any help out there? Thanks in Advance!