There are a few guys on here that continue to run a 7 bolt without issues, but if you're looking for a build up, why not start with a 6 bolt platform? The purpose of going with a built motor is for reliability and longevity. Why not take out one of the concerns (or lessen the concern) from the equation? The last thing you want to do is sink thousands into a block that MIGHT head down the same path as so many before it. Your choice though.

A poorly built 6-bolt (or even poorly tuned) can sh!t the bed just like any other motor, so I'm not saying that it's the be-all, end-all.