I'm getting a supercharged Buick Park Avenue. It is a 94 with the series 1 supercharged motor.

The 93 Park Avenue I have has a NA 3.8 with the 4t60-E (will double check tomorrow) and right now, it won't shift into 4th gear or lock up the TCC. I am not concerned about putting a supercharged motor in it now, but was wondering if the supercharged'* tranny would work? Will the plug in work the same?
The ultra is junk, the frame is all rotted out where its been sitting for years. its a parts only car with a nice interior and doors and other various body parts.

Eventually I might mod up the series one motor. Anything available for it? I really bought it for the nice interior and other parts...

Will a 4T65E HD work in place of a 4T60E? Not typically, you would need to swap computers, wiring, and it would simply be easier to find another 4T60E, or go for a rebuild.

Now, here is the interesting part. The '94 Ultra has a 4T60-HD, not a 4T65E-HD. You will need to swap things over, but I don't believe that it would be that bad. Going from 93 to a 94, you have a different computer system setup, so you may need to move the wiring harness over, and the 4T60E and 4T60E-HD are a little different, with items including differentials, and final drive ratios. I would expect to swap harnesses, as well as one of the drive axles (passenger side I think), and I think the computer may need to be tweaked so that the speedometer isn't funky.

I am by no means an expert, so I will let one of them chime in.

It might be fun to simply do a full drivetrain swap.

You can replace a 60E with a 65E. I've done this a few times. The biggest thing is having a pcm that will control it.

I've done it in a 96 Riv by adding five wires and changing the connector (it'* different) and then updating the programming to run the 4T65E which was available in 97 for the Riv.

Also have done a 97 Bonneville that is NA and had the 60E, the programming was a hybrid to mate the 97 pcm with the 65 programming. IIRC I started with a 97 SC file and brought the NA motor stuff over.

As far as what you currently have..you have a 60 and an HD 60. You should be able to plug that connector right in. Question is.. what will you use for a pcm to run the SC motor. the trans should work well.