Yikes, i too am a procomp dealer, and i will not sell a set of assembled heads, i also will not sell a set of procomp heads for racing (only street use) The Dart 308 steel heads you have (as cast) will out flow any procomp fully ported head. The big problem is the top side of procomp heads as Mark said are cast very thin around the rocker studs and will pull them thru with spring pressure over 200 lbs. Save your money and get a good set of Dart heads, although i would suggest the 345's for a 496" motor rather than the 325's. I've sold doz's of sets of heads without issues for the street, i've been a dealer for 8 yrs. when procomp was first starting out, i don't advertise and don't have a website, just word of mouth.
JMO
Zip.