I have an 87 Cutlass with an 87 GN frame & drivetrain. I did not do the initial swap in 1990, but have learned alot going through the car. My thoughts are that you need to have a complete running donor car to start with. Motor, tranny, rear axle, intercooler ,fans ,(along with specialty brackets & hardware)wiring and the computer. Using a factory GN harness to make wiring installation easier.... my car has the complete Buick dash with Disney Tach & Boost gauge, 145 MPH speedo but the rest of the interior is all Oldsmobile. I'm currently doing a custom GNX style except with VDO gauges. The Buick inner fenders were used for mounting sensors & relays. The Cutlass vacuum brake system was retained but the Turbo Regal AC system was swapped in. Besides the 4.3 Monte, the TR was the only other fuel injected G-body with a baffled gas tank. When the stock GN gas tank did not fit, (Regal & Cutlass necks are different) I ordered a tank and neck separately from Rock Auto, and had the Cutlass neck soldered on. Let me know if you have any specific questions.