will ECM from different motor work?

Hi,
I have a 1995 Chevy Caprice with a 4.3 liter V-8.  I need to replace the ECM unit.  I see some used ones available for the 5.7 liter Caprice.  Will my original PROM from my bad ECM unit work in the 5.7 liter version of the ECM?
Thanks!