the motor looks good on the ad..and should make the 600 advertisied hp no problems...i have owned several 406 in the past....my wife has a cast steel head ( dart iron eagle) 406ci with a 5.20 small flat tappet cam..and it made 480 hp 460 TQ...so you should be all over 600 no problem...
as i said before i have ran these 406 to death..many will tell you the webbing is WEAK and IT IS..but for the hp range you are at ..the motor will be perfect.....you start pushing these blocks over the 750hp range bad things are known to happen to the bottom end webbing etc.....
but again i have ran them all over 700 hp in the past....sold one to a guy in Atlanta that is a member of this board going on 3 years ago and he is still making rounds in the car/motor..6.70's-6.80's in a 3,000 lb car...
just curious how did you verify it was a 400 block ?
thanks brian
__________________
Bjuice..
"I'M YOUR HUCKLEBERRY ! "