I've got some 3800 links laying around I'll have to post here pretty soon. I believe they use a 3.8 flywheel from a Firebird and have it match ballanced to the Buick's Flexplate. Or at least that sounded like the cheapest / easiest rout to go from what I've read. Someone is doing custom flywheels but they're to the tune of $300-$400 as I recall. I haven't read about any kind of a direct swap from another vehicle though that's ballanced correctly. I'll dig up the links and post them later today or tomorrow a.m.

Chris Enos (Chino, CA)

'91 Isuzu Amigo "Rover" (Camaro 3800 swap in progress / 2.25" exhaust)
....(SOA / Custom rear bumper / CB / HAM)