I placed an 87 drive train in my 84 T-type. I also kept my hydroboost and my 84 ECM and wirning harness. The hydroboost was 20 years old before I had to change the master cylinder. The booster is still running strong. Thats a lot more than I can say for the power master system in my 87. I am using the 87 power steering pump in much the same way the original 84 pump was used with the hydroboost. Yes there was some work in getting the harness work on the 87 engine. I did eventually find a used 87 harness and ECM used. I would recommend using an 87 ECM. Only because most chips are written with the 87 in mind. Power will need to be wired over to the fan relays because the stock 84 fire wall fuse terminal block does not have the connections in fire wall connector to source power to the fan relays. You will have to find a new home for your fuel filter. Depending on the shape/curve of our transmission dip stick tube you may need to replace the tube and dip stick also. Your AC lines change. Your radiator will not have the oil cooler. You will need a power steering resivour and bracket. I believe I had to replace the throttle cable. You'll need an electric fan, new down pipe, water hoses, heater core, nearly all the engine sensors, coil pak, ignition module, air dams under the bumper, alternator, plug wires, brackets to hold the 87 harness against the heater/AC box. There more but this is all that I can think of right now.
I'm sure as your project moves on you'll find the items that I forgot to mention.
may just get a bit of heat shrink tubing on each of the wires since I've gotta extend it anyways. If you have to make repairs, use solder and heat shrink or liquid electrical tape. Don't half ass the job, it'll run like an OE harnees.
