Purple Shaft or NOT?

I'm no fan of MP only because they seem to be made by a bunch of drunken hippos. If it was me, I'd run a cam with similar duration at .050 but in terms of lift that cam will open the valves about .465" because you lose a bunch due to valvetrain design. If you have power brakes you need to keep things smaller... to a point. Assuming you don't have power brakes I'd be looking for something more modern, with a faster rate of lift, and advertised lift around .525" or more. Something like the 60405 Lunati or the XE275HL. The pistons are close to 9.5 but you have to have the block square decked and the deck height set to zero, plus have the head chambers cc'd after the valve job to make sure you have a true 9.5:1. For my builds I like the Holley Street Avenger 870 vacuum secondary.