48degree blocks and heads
Follow these links and some good reading on the R3 blocks, head setups etc.
big bucks me thinks!
I was going to go this route, but I could not get any type of exhaust to fot the heads I wanted to run in the 64 Dart.
http://www.shadydellspeedshop.com/faq.htm
Take a look at his site, he has a lot of very good info on the heads types, configurations etc. As far as power goes I know several folks that have had them do head work and it has been very good.
Also BJR is very good and I am sure knows a lot about this stuff too!