id say a 5K turbo would be heaps of fun and pretty straight forward to build up for one of those rolla's, a mate of mine just acquired a nice datsun 1200 turbo ute with a 1400 intercooled carby turbo setup which would be fairly similar. Its quite easy to setup if youve got a ilttle bit of time or $$ to throw about, ancd the results are quite impressing .
Or you could simply just transplant a 4A-G, 2T-G or 3T-Gte in stead which would be almost just as simple, give or take a few issues. Or if youve got heaps of cash ive heard of those little starlet gt engines going in stuff?? any thoughts, peace