[RACER X #99]

If you are talking serious small block HP 500+ don't screw around with any two bolt blocks. A stud girdle is just a band aid. Go for the Dart or the Ford racing block with the four bolt mains. All the serious HP brand X guys have been running 4 bolt blocks for years it's about time Ford and Dart made a good engine block.
If you just want a nice street engine 2 bolt is probably good enough.

Cranky