I have used a few different Junkyard PCMs, some have worked after adaption routines, some have not. Many can be re-used after a complete rewrite, but that requires programming capability for the original and replacement PCM. I have a stockpile of them right now, in fact.
1999 GLS MP90 supercharged / 2003 GL MP62 supercharged / 2004 GLS stock
Magnuson MP90 / TOG's / 3 in. Magnaflow exhaust / MSD ignition / LS1 MAF / Racetronix pump / HP Tuners / TCE 68mm TB / 36 lb Inj
= Best track time: 12.951 @ 104.48, 1.839 60 ft. (Beech Bend Raceway Park, 11-23-13), 50 Deg. F