All the engines are the same from 83-89. The Tbirds and SVOs from 85.5-88 used larger injectors 35 lbs hr instead of 30.Also the 87-88 TC and 85.5-86 SVO had a larger VAM.
The 87-88 Tbird used a smaller turbo "IHI". The 85.5 up cars all used the square intake but the only one that used the short square intake was the 87-88 TC and everything from 85.5 and down to 83 used the Inline intake.
And about the only other difference I can think of at the moment would be the earlier cars some used dual fuel pumps and they had 2 different T3 turbos they had a .60/.63 and a .60/.48 .
And if you get an engine with and inline intake you can put a square intake on it but you have to drill and tap one hole in the head for it.
As for stuff needed for swap. As stated you will need harness,ECU,Engine,VAM and high pressure fuel pump.
As for swapping parts off for the swap the only thing I could see maybe being a problem would be the intake height. And then you would need the intake/fuelrail (Depending on what intake your engine started with) off a 87-88 TC as it was the only car with short square intake also you will need the valve cover because it has a dip for the intake to clear and not hit it.An if you find a 87-88 TC in a junkyard and you grab the intake get the ECU, large VAM and Injectors since this car had all the best parts minus the larger turbo.
Oh an you have to put a pinto 2.3 oil pan, pickup and motor mounts on the engine but thats should be a no brainer.