[Sprocket]

What are you running on the exhaust side?

For 15 years, I ran the following combo in my '70 GP: 455 +0.030, KB pistons, stock crank and rods, Ultradyne 280/288 (223/231 .463/.485, 104 ICL, 110LSA), 98cc 4X heads with competition valve job, Edelbrock RPM intake, Holley 4150 750 cfm Street HP, short branch Ram Air exhaust manifolds, full 2.5 mandrel bent exhaust with x-crossover, TH400 w/13" Continental, 3.42 rear, 28" tires. Stock fuel system. No porting, no port matching, no balancing, no blueprinting.

That combo was good enough to propel me to 13.0 at 99 mph in triple digit heat. The car produced incredible torque, frankly too much torque, but was all done really by 4800 rpm. It was quick but also could easily nuke the tires.

Similarly, I ran the following combo in a '78 Catalina wagon (similar curb weight to the GP): 455 +0.030 TRWs, stock crank and rods, 041 cam (231/240, .470/.470), stock lifters, 90cc 6X heads with same competition valve job, Edelbrock RPM intake, short branch RA manifolds, full 2.5" mandrel exhaust with crossover, TH350, don't remember the converter, 3.08 rear, 27" tires. Stock fuel system, no portwork, etc.

Running head to head with the GP, that car was not as quick early on but did not take long to blow by it and keep going. Even with the bigger cam and less gearing, it had monstrous torque and really did some damage on the street! At freeway speeds, it was a real beast. Seeing the embarrassment of either getting smoked or not being able to run away from a maroon with red interior station wagon was fun to watch!

Both ran on premium pump fuel without problem. IIRC, the GP was about 9.25:1 and the SW about 9.5:1, and either could be +/- a bit.

I would think that the ported heads you have would solve the breathing issues that my GP had and provide upper end power without resorting to a larger cam the SW had. Add your larger cam and your heads, and it sounds like you have a winner.