You find prom numbers in the GM parts books.  I'm not sure where Joel got his.  Some aftermarket manuals may have the listings. 

Joel, sounds like there aren't too many proms, if so would you be able to list the numbers for me please ?
Or scan the page(s) and email to me ?

cdowns@clear.net.nz

I have the GM parts book. That's where the info is. Some of the part numbers may have been superseded, but will still cross-over. The real problem is, most GM dealers are NOT gonna have any of this stuff anyway. However, there are some Vendors that will have some NOS stuff. Or...it's good to have the nums to verify what you have, or what you may be buying.
Chris, I'll e-mail you the list of PROM #s when I get home...I don't have the disc here.

81 Y w/AT Calif 1225432   Calibrator PROM (code 81140H)
81 Y w/AT Fed 1225430   Calibrator PROM (code 81180D)
81 Y w/MT Calif(1st Des) 1224869   Calibrator PROM (code 5839CF)
81 Y w/MT Calif(2nd Des) 1225433   Calibrator PROM (code 811040J)
81 Y w/MT Fed(1st Des) 1225310   Calibrator PROM (code 6084FN)
81 Y w/MT Fed(2nd Des) 1225434   Calibrator PROM (code 81080K)
(AT=automatic trans MT= Manual trans Fed= Federal emissions Calif= California emissions "Calibrator"= "Chip" PROM= Programmable Read Only Module)


It's WAAAAY past me bedtime....I go sweeepy now....

I'm awake now....
These are the PROMs listed for the '81 Corvette, and as I stated above, they all work in the same ECM for '81, so...only one part # for the ECM.
It appears that 2 of the PROMs are updated programs for the manual transmission cars(2nd Des = 2nd design) for both Federal and California cars. The automatic cars were not changed.
This should get you the correct chip/prom for your '81 Corvette, Chip. Other vehicles lines may not have used the same programs, so they may not work properly in your Corvette, and that may be part of the issues you are having with the e-bay stuff.
hthAdams' Apple2008-09-16 05:10:44

Thanx for that Joel. Rather weird that the Proms I have don't match any of these numbers ???   Whats with that I wonder !!

Chris

Bubba was here.   And he changed PROMs.     It may be difficult to find the right one, but it's necessary. kstyer2008-09-17 18:29:51

The parts book is current as of....1983!
However....I have ordered parts using the part numbers in this book with no problems...as long as the dealership/vendor actually has the part. And, as I stated, and Ken re-iterated, some of these numbers may have been superseded, and/or discontinued...