This video is where I determined that there are no differences between the '89 and '90 model GT's...
The '90...I can't tell any difference at all. Remove that hideous rear spoiler and it looks identical to the '89.
I have to wait on the repair of the lift in the back shop before doing any major disassembly of the car. I have not received any detailed feedback as of yet on specific parts, but from what I have seen thus far I'm leaning toward the MM full length subframe connectors and 6-point rollbar. I'll fabricate my own driveshaft loop and weld to the subframe connectors instead of the usual bolt-thru the pan variety. I'll need to talk to someone in the know about specifics like upper/lower control arms, springs and reinforcement of control arm mounting points.