I have a 91 mercury cougar LS with a strong V6 I just bought an 89 Cougar XR7 for the supercharger wheels and gauge cluster. My question for those who know is will it be a bolt on fit or does it require a rebuild for a stock SC? They are both 3.8 L V6.

 

The 91 may need some beefing up of the trans. You can probably get away with easing into stuff and help the trans last longer though. as far as bolt-on fit... it looks like there's different heads for super charged vs not. Same goes for the block. Looks like you'll have better luck swapping the entire engine than putting the supercharger on the older engine. Considering that intake gaskets are cheap, though, it might be worth checking more thoroughly than just my looking up Ford parts.