Being I've owned and raced both RAM AIR V and RAM AIR IV engines, I think, I can give an honest answer. I've raced a stock RAM AIR V engine it
had the stock solid lifter cam, intake and distributor, the only thing aftermarket was a set of custom headers. The motor was in a 3680 lb 68 GTO and ran 10:87 at 122, I had a turbo 400 with a 3500 stall and a set of 430 gears in a 12 bolt rear. I never lost a race on the street with that car it beat 427 Chevys, 440 Mopars and every other car that came up to it. The only car to give me a run for my money was a Ford Thunderbolt with a 427 in it. The heads on a RA V are the best breathing heads every made by Pontiac the problem with the RA V is that Pontiac did not have a big enough engine for this head it needed more cubes than 455 to take advantage of it's wide ports. Second the RA V was sold in parts from the dealer and no one makes aftermarket parts for it, you have to have everything made custom other than the few stock parts floating around. As for the RAM AIR IV it has the best breathing heads ever placed on a car from the factory. I current run a RAM AIR IV engine with cast 722 heads in my 68 GTO and it does mid 9's in the 1/4 mile at 139 mph. The availablity of parts for the RAM AIR IV are Excellent and it seems to be easier on parts than the the big block Pontiacs. Let me leave with what Pontiac called this engine " KING OF STREET" There plan for this motor was to compete against the street hemi, before insurance and the 70 market killed it.