There's nothing better about a RS1600i head to any 1600 cvh head of that period.

In all fairness, there's nothing trick or worthwhile about the RS1600i engine whatsoever that should encourage you to start with that engine. It is for all intents and purposes a std 1600cvh with a solid lifter cam fitted. (Yes I know it has unique anciliaries but they're only special if you're keeping the RS1600i car as an original car)

My recommendation is get yourself a late XR3i hemi engine (i.e. 86 - 89) and modify that. Usual route would be big valve ported head, solid lifter cam, set of throttle bodies, decent 4/1 exhaust manifold, H section con-rods, set of forged pistons and around 12:1 C.R. Good for 160bhp. Happy days!