Speed Pro/ TRW made several different versions of the forged flat top pistons with no valve reliefs, some are for the 1968 to 1970 HP motors and some are the later 1971 and on lower compression motors. Do you know how low the deck hieght is in your motor or he actual compression ratio? If not I would recommend buying a set of the 440 Source Stealth aluminum heads, they are close to 80.CC instaed of the 90.0+ CC of the stock uncut heads, that change should help a bunch if your pistons are down in the hole .050 or more I have dyno tested a bunch of 440 motors similar to yours with 906, 346 and 452 heads, it is not hard to make those combination make 475 HP + on pump gas As far as what parts I would use to help you reach your goal is the Stealth heads with a decent set of adjustable rocker arms and pushrods to match, degree the cam to advance it 3 to 6 degrees, if you haven't already and then look at tuning that combination to its max. BTW, I really don't like any of the Mopar brand cams, I like and use Comp Cams If your interested in changing the cam also PM me for more input