Well its possible, but quite a lot of work is involved. The smaller engines i.e 1.1 and 1.3 are mounted in the engine bay at a different angle to the larger engines i.e 1.8 and 16V. Consequently the left hand engine mount (as you look at the engine bay) is in a different place..........I had a donor car and cut the bracket out of the chassis on that and welded it into the correct position on the project car.
Gearbox, gear linkage, drive shafts, wiring loom, exhaust even the radiator will all be different and also you'll need to install the electric fuel pump, accumulator etc.
I would, at the very least, consider buying a donor mk1 GTI for parts.