Personally I would just build the 390 to run on pump premium. With gearing you should be able to run around 10.8:1 with flat tops. A decent big solid flat tappet and a bit of head work to the Edelbrocks and you're around 550HP on an honest dyno.

The 390 block will become marginal around the 600 HP mark - so there is no reason to push much higher - it's not really cost rational to add cros bolts to a 390. RPM is not a problem - we've run the stroker stuff past 6700 and up to 7000 with regularity. Its just that most of my 390 builds don't ned to "go there". These are generally pretty torquey and peak around 5700-6200 in street combos.

I can be a challenge to get on the phone sometimes. Kind of a "one man band"...but busy is good. Woodward Dream cruise this weekend...