It sounds like the "cam lope" you described in the original post was actually a problem with the cam profile! Bad news! Do you have any idea how much mileage the engine has since the rebuild? If it's pretty recent, less than 50K since the buildup, for instance, it would be worthwhile to install a new cam and lifters. More than that, and I'd suggest doing at least an in-the-frame rebuild, rings, rod bearings, valve job, etc., as well as the cam change.
I like the Comp Cams 260H cam for a little bump in performance without seriously affecting low speed torque, gas mileage, or towing ability. It's got a very slight idle lope, more like a slight miss in an engine with a factory-original cam. This smooths out at 1,500 RPM or so, and that's where I start doing dyno pulls. By 2,000 RPM or so, the torque comes on like a kick in the pants, and it pulls strong to 5,000 RPM or so. Good for street use, without adding a high-stall torque converter or tinkering with the rear end ratio. A 3/4 ton should have the right gears for that cam to come alive nicely at low to midrange throttle.
Jerry
