Which he's probably not going to break running less than 500 hp, so what?
The previous owner bought the axles, the 5x4.5" pattern is useful for a lot of reasons that have nothing to do with strength, and the disk brakes work better regardless of the horsepower.
Unless he's building a dedicated drag car on slicks or running a boatload of horsepower I wouldn't be worried about the 741.
The biggest concern I'd have is that the aftermarket axles are the dumb kind with the 5x4.5" bolt pattern, but the SBP axle flange offset...
