I'll through in $0.02, since I have a nickel in the pocket. Today we do have engine options that are really cool. The success of the GM LS swaps, now the Mopar Hemi swaps. So many packages that have been designed so we can put new technology in old school cool. The LS swaps became the rage, now we see builders begin to keep the older blocks again. I see the same with the Mopar crate Hemi, it'll ramp up, then settle out.
I have a '70 Super Bee 383. Thought about the engine choices a lot. I decided to keep the 383. Plenty of ways to build a perfectly respectable street engine with 400 horsepower. I want some benefits of new technology so I'm looking at the Holley FI systems to run, with timing control. For me, the car was cool when new, so I'll help it a little, but keep it mostly original, enjoyable, and reliable.
Have fun with the RR, I'm sure it will real nice whichever way you go.