SuperCharger
Reply #3 –
It's the same basic engine, but the '89 block is a different casting, there's some subtle differences in the heads as well.
You could probably get by studding the block for the heads, instead of using the TTY bolts, and using a good quality head gasket set such as Fel Pro...Definitely have your heads check for straightness and have them resurfaced/milled as necessary. You may have to use the internals from the SC 3.8 in order to lower the compression to be friendly with the forced induction...I'm not so keen on the different pistons and rods, but I DO know they used a different combo starting in 1989.
HERE is a great place to get started if you're serious about beefcaking your 3.8. :)