The import (Black tappet cover) motors apparently run 45mm and South African motors run 43mm. This is what I read on VW site.

The Toyota motor is 1600cc but remember it has more modern valve train and also revs to 8500rpm. The VW cylinder heads in my view are still dinosaur designs.
As stated previously, go quad throttles. How much will it cost to choke the Toyota throttles? Is it as simple as just fitting a sleeve? I would have thought that there is more to it.