The G10 is a possibility without body modifications, but alternative differential would need to be sourced as the gearing would be too low on 13" or 12" wheels. Alternately go for a larger wheel size with possible body mods..
I've measured the G10 engine and the lack of one pot and being a single cam head, there is a chance that it may miss the offside headlight. There are other challenges in that the cam cover ends up under the bodywork, so you need to drop the subframe to get the cam cover off! The answer on the Mk1's and is a flip front.
The moulds for this modification are in Ireland I think. I don't have the fibreglass skills to attempt this at the moment, But somebody else may have, then I can continue designing subframes. Aitchi has found some rather excellent twin head lights that would fit the bonnet quite nicely
Headlight link: http://www.ebay.co.uk/itm/270802585102? ... 1423.l2649
Alan