I am rebuilding a 454 for my Crewcab and I am looking for some advice before I begin. The engine is from a 74 Chevelle/Monte Carlo and appears to be totally stock. The engine bore is still 4.25 and the heads have 2.08 Int/1.70 Exh valves. These are the 781 heads. I am looking at doing a .030 over bore and going with a cam approx. 208/218 dur and 485/515 lift, something with lots of low end grunt for towing and around town driving no need to top 5000rpm. I am really running into a problem deciding what to do about the heads though. The stock valves are in good shape, so should I reuse them and maybe do a small porting job to gasket match and remove casting flash from the ports. Or should I do the port job and step up to 2.19/1.88 valves. I know I will have to get some new springs to match the cam. Any of you that work in a machine shop able to give me an idea of what the machine work will run to check the heads for cracks and to upgrade to the larger valves? Also anyone with desktop dyno or such able to tell me what I would be looking at for hp/tq with this set up?