the price of heads keep going down .how good are they ? the patriot performance heads for as-cast are 460.a pair .so why would you play with heads that are old casting that could be well used ? i have got in to this before i have a machine shop would be happy to reguide put new seats in .cut out for bigger valves. mill and do a 3 angle valve job on a old worn out set of heads .now the new head s could need a tune in on all the stuff i listed but still your getting a better flowing head .i still think your going to have more in old gm casting then a new set it is a time and money thing. if your time is worth nothing then stones sand paper and other supplys will add up . you still will have to cart them off to the machine shop .when done you have a old out dated heads that could flow not any better then they did stock with a very good valve job i still think this is were alot of power is on how the seat is formed and the valve flows and the short side radius of the port along with the chamber and how it much it shrouds the valve