.060 . usually puts #5 or #7 through the side of the block on anything higher then a 340-2 block when when hooking up with alot of torque. Use a front and mid plate. Standard mount locations increase the possibility of block flex.
All 410 sprint cars running standard SBM's use 340-1 blocks. They are the strongest and always sonic test the best with concentric wall thickness.Also stud every threaded hole in the block. It does stiffen things up. Alluminum heads make the flex worse.
This is just my experience with standard blocks. I lost many and saw many losses due to this. If your motor and car is a pig it won't matter.
