If you haven't found the source yet....you should check out
924Board.org :: Index or
Porsche 924 Garage & Register home and post the question over there.
I have a 87 924S, I love the car, but the engine is quite different than the 81 924, so I will not venture down the road of how difficult it will be to awaken from its slumber. Do a little research on the 81 924 that is being offered and its option codes.
I like the cars that you are considering, the MKII GTI/GLI are fun little cars, as are the E30s.
Happy Motoring.