John, when you say you have seen a lot of stuff about "good 2-bolt mains", where have you seen this??

As far as I know, a 2-bolt main block is a 2-bolt main block. I've never experienced good or bad.

A 2-bolt block will take just about anything you can throw at it up to about 7,000 rpm's and/or 450 hp in my opinion. Above that, you may want to consider a 4-bolt block.