5.2 magnum options

ok, I put a 5.2 magnum in my 66 valiant. it has a 904 w/a small stall 22-2400.
I have a miss that wont go away. swapped carbs, and the entire ignition system with zero change. it was rebuilt before I got it ( about 8,000 miles ago ). I have a feeling this is why it was pulled. im thinking it has a sticky valve or two.
do I just upgrade to the EQ heads? will porting help the stock lower end?
any suggestions for a cam? it currently has a larger than stock comp computer cam ( not verified )
I am running a 600 holley on a air gap knock off intake and have a set of shorty headers to install when it goes back in.
really just looking for a cruiser with some grunt that we can enjoy. car barely was used last year because of the miss.

THese motors are extremely sensitive to spark plug wire routing. There is even a factory service bulliten for this issue. The motor will miss if you route them wrong.