At what HP /rpm level are billet main caps and or stud girdle needed?

I won't disagree with you, but honestly he would have more in a block than he probably would in this entire engine combo. I understand for strength and security, it's just a fat chunk of change for a mostly street engine that will probably live below 5k rpm it's life.
The aftermarket big block stuff is a little pricey I will admit, it would be nice to see them get sub 4k range