It's definitely different strokes for different folks. Power is not what it is all about when owning these classics.
Decide what you want to get out of the car before buying engines. Remember going RB will be sump, fuel, diff ,gerbox mods. Plus you'll have to open up the tunnel to fit a larger gearbox. Then you will have engineering headaches if done legally.
You could put some triples on the engine, better camshaft, exhaust and have a nice car. If you want to go a little further you can do some piston swaps to bring up compression and/or port the head. Again, just depends on what you want to do.