Thanks for the replies guy. I'm looking to build a 625-650hp engine to help get my car to run 6.50s on a hot muggy day to be able to run a 6.50 index class. I've been running 440's for years but just stock stroke stuff and nothing over the top. I have both 400 and 440 blocks. My gut tells me to go with a 400 block, but my wallet says 440 since I would need less parts. I think I would be fine with a 440 as I'd like it to run on pump gas. I'd like to shift at 6000 and never turn it over 6500. But if it would crack than I'd be kicking myself...Decisions decisions