TI302

how much of a mess am i getting into? ive got an 85 carbed 5.0 5speed, looking to put into a 90 4cyl auto. ive got both cars, wiring harnesses and all. can anyone give me some heads up on what im looking at getting into so i can do some research before hand? for example what the hardest things are (adding the clutch and pedal, splicing or replacing the wiring harness). and since i have both cars does anyone know the difference in suspension, 85 GT vs 90 4 banger. both cars are complete. id like to build the 85 being a t-top but the rear frame has some serious rot that scares me.