These rods are rated for 750hp

The purpose of that rating is to allow Buffy the phone girl to answer your question in the shortest possible time. "This is the rod you need - you expect to have 750 hp, don't you?"
Would a 40 psi 1000 hp LSX turbo engine break those rods? Not at 5,000 rpm.
How about a 400 hp engine at 9,000 rpm? Every time.

What breaks a rod:
1. RPM squared (8,000 is not 33% more than 6,000, but 78% more)
2. reciprocating weight (direct proportion: 2 X gram weight = 2 X as bad)

Not sure?
If you exceed the critical rpm (generally a function of the fastener size & quality) the rod will break with the ignition off.