How many rpms are you turning and what speed. Your engine looks like a torque monster on paper. Maybe you should try going up in pitch on the prop. It might be making more power but at a lower or the same rpms.

Its turning a 24 labbed prop at 4,900. Around 68 GPS
in a Pachanga-22.

Personally I think you have selected cam that should make real good power to 5000rpm in your 496 with better flowing heads. The tighter 112° LSA will extend the rpm range vs. the 114° of the 420cam.
With a good set of heads and an intake to match your engine will make a lot more power. Those heads need lots of work and bigger valves to flow.
Is the engine sit in the boat?
Swapping heads and an intake is doable in the boat, a cam change would be a PIA...

Try a 26. It might pull it to 48-4900 rpm.

I agree, now way those heads flow enough for 4900rpm.

Crane says the 420 cam is 112* lobe

http://www.cranecams.com/?show=brows...61&lvl=2&prt=5

Cam Timing: TAPPET @.050
Lift: Opens Closes Max Lift Duration
Intake 5 BTDC 43 ABDC 109 228 °
Exhaust 57 BBDC (1) BTDC 119 236 °

Maybe I'm not doing the math right, but I believe 114°LSA

Pat,
You are correct.
109º ICL
119º ECL
114º LSA
Bob

With out going to a roller cam
and
my current cam will work,,

Getting back to my original question
What heads would you select?

The engine is in its winter home ENGINE STAND

Personally, I like the Brodix 3x CNC. They have made great power for me and have been recommended by many engine builders.
You might also look at the PRO 1's from Keith Eikert. They are advertised in the classified's for 2k a set complete, I think.