Probably near any front driver donor powertrain/suspension could be moved to the rear, but I fear a substantial amount of enginering might be involved. Not for beginners, but loads of fun for those with the equipment. Some things to watch out for might include:
Removing the caster from the set-up. I hear it does strange things to the handlilng in a rear engine application. Anyone know how Subie builders do that?
Height of the total engine package. Will it fit under a speedster body shell?
Track width. How you gonna widen or narrow the rear tread to fit the fenders?
Cooling. A front radiator has been done before, but do you need additional air induced cooling in the engine compartment to keep other components cool? The headers are back there with no air flow over them.
This is really getting away from what kit cars are all about and getting into the street rod realm, but that ain't bad at all, except for the money required to play the game. I've always thought it's really too bad, with all that talent out there, that more people can't make "original design" vehicles. Maybe kit cars are just the springboard needed to step off into the new and unknown. And yes, I have seen at least two different 911 Porsche bodies with blown Chevies sticking up (way up) through the front bonnet. Kooollll.