440 Head and cam question

the 906 head will flow a lot better than a 516 head. you can cut the head surface .025 ,will help with comp. a motor is an air pump, more air in= more power. as for duration, mopar states stay under 280 advertised duration. look at your 906 head, under side is casting number, next to it is a letter. should be a M,R or F. the F is the better flowing casting. the M is next best.