I would try the RPM first with the new mods and then decide if you want to change the intake or not twocents
If yo decide to get rid of the RPM I have a new motor with a Mopar M1 4150 intake on it that I would be willing to swap for your RPM if you pay the shipping for both work I had this motor(400 block with a 440 crank and rods, 451 C.I ) on a DTS engine dyno with a Holley HP 950 carb and it made 489 HP on CA pump swill in Ontario, CA on the Carb Shops DTS engine dyno with that intake work
PM me on here if that is something you want to do up

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)