My 3.6 died.
1990 PT engined. UK car.

I have fitted a 4.2 (1992 ABH engined, UK car), and initially used the injectors and rail from the ABH. I have since gone back to the original fuel rail and injectors.
The engine fired up with no major issues. I do have a few minor problems which will be looked into when I get a chance to have it serviced.

In addition.
I used the original Hydraulic pump, and Air con pump, to avoid losing fluid or gas. For expediency.
Both starters worked fine, so one is my spare.
I left the knock sensors installed on the ABH as they came from the donor car.
The original PT wiring loom connected up to all the same locations on the ABH.

I pretty much managed to do the whole thing single handed, using mainly a trolley jack to get it apart.

If they aren't already done. Use the opportunity to check and replace brake lines while the engine is out.

Anything else I can add, or provide insight into, PM me.

Mark

85 WR quattro
90 V8 Silver, 91 V8 Black, 93 V8 Lago
93 100e quattro V6. Titan, i think