RST conversion (EFI)

cheap and cheerful, plenty of tuning potential and parts are readiliy available

I know a few people who have gone the "pumesta" route, they seem to like it at first but soon get used to the power which you are pretty much restricted to unless you spend a lot of cash. A good EFI power plant would make an easy 180bhp and they are pretty cheap on the rebuild side of things, tuning is not limited at all, only by your wallet

Hope this helps