I have a 91 Xfi and love it, just fix what you have or find a good Metro shell. I wouldn't try to swap into a different car it would not be worth your time. There are not too many cars on road as light as Xfi so that drivetrain would not power it down the road too well.
There is alot of useful info for those cars on here.
Project 60/60 Xfi
Mullet's Metro project
My Xfi build.
Lexan headlight covers