Just as Mark says, i have a 400 on my engine stand 4 bolt 406", and i drilled and tapped the steam holes, and the big water holes. I also have a 400- 2 bolt in my Malibu. 377" and it's been in the car since 2004, more than 200 passes on it and never been tore down. It has 13.5 pistons and on alcohol. I use studs on both the mains and the heads. In fact i use studs (mains and heads) on every engine that i have, even the Dart little M blk 434" that's going in my car in the next few weeks.
I've seen too many helicoils in blks in my life to not use them, i also use Copper or MLS head gaskets only.

Zip.

400
 

I had bolts, which I know put more stress in that area. Studs might have helped in this case.