Pre-Facelift 316 carb to Facelift 325 conversion help please

[Badger0068]

I know this has been covered a few times but there is so much info out there I would just like some definitive answers..
I have a 1987 316 carb, pre facelift model and I just bought a 1989 325i facelift model that I want to use as a donor car for my 316.
I know it is pretty much a straight swap to get the 2.5 engine, gearbox, prop, diff etc in my 316 but what else needs to be changed? I read somewhere the fuel tank may need to be changed as my 316 is carbed, not injection.
Also I read that the wiring could be a bit of a problem as my 316 is pre-facelift and the donor car is facelift...Can someone elaborate on that please?
Anything else I should be aware of before I start?
Thanks for any help

[Badger0068]

Sorry for the noob questions, I'm useless with electrics. My mate is doing the wiring for me, he just wants to get as much info as possible.
I took the dash out of my donor car today and I will be putting that dash in my prefacelift, so do I want all to take out the whole loom out from behind the dash and put it all in the prefacelift in order for everything to work? Or are there parts of the prefacelift loom I can use?