Well, I like the combo Im running- I have 31's and 4.10 gears. When I rebuilt the engine I bored it 30 over and added the 410 Comp Cam, 70 mm maf, 63 mm TB , Borla headers, the heads were port matched, and cleaned up a bit- not real porting, the combustion chambers had the sharp edges removed, intakes(upper and lower) were gasket matched and Im running an Apten chip.
The bottom end feels really strong, a concern if you wheel a lot. But rev it over 2500 rpms and it will really pull well to 4500 or so. I dont normally see much above 4000 rpm anyway the way I drive. I do need to adjust the shift points on my trans- it shifts way too early. With my tires and gears my combo seems to work fine. Im worried Ill see some losses when I step to 33s , so I may have to gear down some more.
With the 37s and "only" 4.56s Im thinking that the 422 cam wont give you enough lower end. Its not just the lift, but the bigger cam has a bit more duration which bleeds off low end power. You have to remember that its not only your cruising rpm you need to worry about, its also the power that gets you there. With lower gears you can err on the side of a bigger cam, but with 37s the 4.56s you run are canceled out in my mind . If you had 33s with the 4.56s then I could see running the 422, but the bigger tires may keep the rpm range too low for you. I would suggest the 410 cam, with money spent on the heads- port work inthe bowl area, and a complete polish job to ward off detonation with the bigger tires.
The bigger 422 cam most likely would like more compression which may help pick up any losses on the bottom end. One Idea to run the larger 422 cam is to use the late model heads to increase static compression. This may be a good option, but I would definately have the heads polished since the potential for detonation may be increased. This is one idea I played with when I was rebuilding- but shelved basically because the machinist did work on my old heads before I could make a decision. It still sounds like a good idea, maybe Doug would have some real world input.
Now with all that said Ive never run the 422 cam so I dont know how much bottom end it will lose, but the guidance I got when I was looking fior cams was the 410 moved the torque up about 300rpm, and the 422 another 300-400 rpm - so 600-700 total on an engine that doesnt see 5000 very often seemed like a lot to me.
If you go with the rv cam, and want to step up later you can get the 1.6 roller rockers that Doug904 sells which should increase the lift by about 8 percent, and add a few degrees (4 or 5 maybe) of duration.
