I plan on getting the 424 ci 403 short block together next year. I have ported #6 heads with positive seals, 2"/1.625" valves and filled crossover's. Other than new springs for the roller cam along with new positive seals, I will probably leave them alone. Problem is the 55cc chamber, it puts at 11 to 1 with 0 deck, aiming for about .010" the hole at most. Being a 403, I plan on enlarging the chambers close to 403 gasket around the valves an polishing the chambers to add 10cc. That will drop it to 10 to 1 or slightly less. I plan on running an appropriate sized roller cam, whatever Mark(Cutlassefi) recommends. I went 9.6 to 1 with crappy .065" quench and the small 204/214 cam in an Olds 350 using these heads, it sucked on 91 with day to day driving, pinging, I even put in NGK 5670-8 plugs, extremely cold and I will reuse them. I plan on Chinese Stainless full length 1 3/4" headers, Summit 2.5" X pipe exhaust with either Hooker Maximum Flow or Magnaflow mufflers, a 2500 stall Hughes converter, a junkyard TH350C with a Transgo shift kit and the stock 2.78 open with maybe a Lock Right or similar. Thoughts?