2-Bolt + Main Girlde Question

I don't think a main girdle will make the block any stronger. A block will
handle what it can handle. I'm sure it will help however.
If you plan on pushing the limits of the stock block, and are looking
for cheaper ways to help it live longer, mabey you should forget those
worries and just get the new Boss block. At that point you shouldn't have to
worry about the block for quite a while. That's just my suggestion though.
 
Everything I've read about using girdles says they do nothing to help with the max your block can hold. That being said, they should help a good bit with salvaging your parts if you do experience a catastrophic failure of the block because they should hold the two halves together.
 
Pretty much any of the after market blocks except for the FMS Sportsman, will give you the block strength you're looking for.

As for the new Boss block... I've not heard yet what machining costs are going to be. It looks very similiar in contruction to the Dart Sportsman but FMS historically, seems to require the greatest amount of machine work. I'd probably wait until someone came along who's tried one.