Anytime you can tie everything together it will strenghten the integrity of an engine, how much 'more' HP you can throw at it is debateable though.
It certainly would be stronger with one than without IMO.
I bought one and planned on using it on my 454 2 bolt block but I ran into fitment issues with the oil pan, after purchasing three different pans that would not clear the guirdle, I ditched it.
I would say 750- to 800 HP is about the point where you'd want to start thinking about getting a aftermarket block, stud guirdle or not.
Goodluck, Cp