well, if you want an underhood capable ECM, look for a 1227727 or 16149396.
if you want one that can only mount in-cabin, look for a 1227730.
1227727s can be found in any 2.8 or 3.1 equipped 88-92 W-body, and 90-91 5.7TPI corvettes. the 16149396 is essentially a slightly upgraded 1227727, and can only be found in W-bodies equipped with the 3.4 from 1991-1993, or equipped with a 3.1 from 93-94(keep in mind, 3.1, not 3100).
a 1227730 can be found in a LOT of stuff... but most notably, the 90-92 V6 F-bodies, and nearly every(if not all of them) 1987-1994 FWD GM vehicle that is not a W-body that has a 2.8 or 3.1.
preferably, find an ECM that already has a MEMCAL in it for a 3.1 application, since it'* knock filter will be more tuned to the specific knock properties your engine will have.
1995 Monte Carlo LS
3100, 4T60E, OBD1 Conversion...for now, future plans include a 3900, T04E-46 (Knock-Off) turbo, and a F40.