231 was usually a turbo buick motor, they didnt make to many of those.

3.8 buick woulda been much later on say 93 and that engine looks to old for that swap. As thats when they were in f bodys.

I would say its out of an older buick, it was a fairly common swap way back when but it has vibration issues.

1996 T100, Mickey Thomson Classics, Bridgestone Dueler AT 265/75/16, custom offroad KC's.