One of the first motors I built for a customer was a 383 motor in a 1963 dart 270 two door hardtop with a 727 and the stock 7 1/4 inch rear end
He wanted a bad pump gas street motor in 1971 so I built it with 12.5 to compression , a Isky 505 T solid roller cam with isky rocker arms and a Edlebrock STR low deck manifold with two Holley 650 or 750 D.P. carbs(CRS now ) and a set of Hooker street chassis headers that they use to make for the early A body cars with a B or RB motor in them. He was suppose to buy a B&M 069J converter and a good electric fuel pump before racing or driving it. He lied about that
that motor was a dog below 3000 RPM but it would really set you way back in the seat once it started to come on
Your cam sounds like it is quite a bit tamer than his was, how does it drive for you?
Is your car a Belvedere Two ?
I almost forgot that Plymouth went to the C bodies for the Fury line in 1965