[byron w]

Brent,
Is this going to be a race only motor? If not, probably 95% to 98%
of the time it's going to be in a much lower RPM range. I have turned stock 390 short block(cam and heads of course) 6200 to 6300 many times years ago and never hurt the lower end. The lower end was and is an FE's strong point. Build what you want and don't worry about the occasinal blast to 6500. Just be sure and use good valve train with hardend rocker shafts.
Enjoy,
Byron W.