Would it be easier to efi the ignition/injection system from a frst?probably quite a few about now nice and cheap,could work out a lot cheaper.I'd imagine a carb turbo would be appalling on petrol also.

Certain you can fit the bigger head almost straight on iirc?sure boys used to do this back in the day?that way,a frst head could be bought complete with inlet manifold/engine loom etc and wired up from there?