Is this an easy conversion? Assuming wiring is the only area to modify as rest of parts can be got from the donor vehicle?

 

If you are using a donor car just put all of the bits from one car to the other. Assuming the donor is an Escort RS Turbo.

 

we did it to one of my brothers rs's after it was written off and it was pretty straight forward

 

Tank,engine/complete loom,general engine swap bits,fuel system(as yours is carb),remove abs,5 speed linkage(if yours is 4sp).
I'd bolt it all up as one unit out of the other car.
Last one I did (back in 2000!!!) I took the lot down(excluding tank) from the strut tops and steering rack bolt and put it all in one lump,I found that much easier (it's how they do it in the ford factory,I've watched it on a mk 5 fiesta which is same set up).
Generally a really easy conversion,mine fired straight up and ran well.
Also,wiring wise I took the whole dash out,cut all the wires under the drivers side kick plate,re soldered into the existing 3i loom and did it from there but there's far easier ways of doing it now,no t'internet back then!!!
I will say I had no probs doing it that way though.