X O U or J heads on a 416?

" We ended up with 501HP @ 5600rpm and 498TQ @ 4400rpm

With 450+tq from 3000-5750 it will be super fun to drive. It idles at 850rpm with16 inches of Vacuum "
Quoted from MRL' s link.

Stellar numbers and staying under 6000 will help it live a long and happy life I bet.
I thought 500 h.p. might be out of reach.
Great job.