I have had a Mopar engine builder and author, and another guy-a driver running a 440 A-body I saw at the track 9.5s at 150mph BOTH say I didn't need and they don't run a girdle on their stock block 440s or RB stroker in the 600 horsepower range, much less an aftermarket block in that horsepower range.
Regardless of their advice, if I use a factory RB block vs aftermarket, I am DEFINITELY running
this cap and girdle system:
http://www.bcrproducts.com/caps_and_girdle_system.html
So my only question is factory block or aftermarket and that's going to come down to how much nitrous oxide power I may add to my close as I can get to 600 horsepower, and hopefully 650 ft lbs torque motor. 100-150 hp shot is what I'm thinking, as an "oh ****" button, and if I can keep it to that "rare" use, well.....
The other thought is how long will it take and how much will it cost for me to just make use of the power my future motor will have. In other words traction, best tune, time behind the wheel at the track...
It may take the rest of my years just to get the most out of a 6XX HP and torque motor, so adding a little nitrous and the corresponding question of stock block w/girdle vs aftermarket block may never come up.
I guess the last variable would be answering the question "Do I want an aluminum aftermarket block to save a couple of hundred pounds AND the capability to add 100-200 horsepower shot of nitrous?" If the weight savings is literally 200 pounds, and I "think" I want the capability of adding nitrous, maybe that combination can convince me to spend the extra money on an aluminum aftermarket block.