DO you have access to gas to run closed chamber? You will be increasing compression a good bit. Nothing to write home about with the 906s. Chrysler put them on everything from 383 2bbl grandmaw station wagons to 440 six pack Road Runners. They are basically a passenger car head and nothing more. But.....as usual somebody will be along to tell me how much better they are than any other head. Horse hockey. The ONLY HP casting Mopar EVER made for the big block besides Max Wedge stuff was the 915, which is the sister head to the 516. Do some mile port work to the 516, put the bigger 1.74 exhaust valve in it and you're there. But again, remember the compression ratio increase.
