Kind of depends on what rocker arm ratio you're planning to run and some other stuff that you didn't mention.

Assuming you want to go drag racing and you're going to be using gas then I'd think something in the 260/270 duration at 050 would be about right. Maybe something around 0.400 lobe lift.

My 505 motor makes around 800 hp with a 266/272 solid roller that has about .400 lobe lift. I use 1.85 rockers on the intake and 1.70 on the exhaust though. That combination is fairly easy on the valve springs and makes good power but the rocker arms cost a bunch of money.

https://board.moparts.org/ubbthreads/show...part=1&vc=1