If torque is what you want, start with Comp Cams XTREME 4X4 cam. Even if you don't have a 4x4, look at them. Go to www.compcams.com the page numbers are 102 and 103. Or you can give them a call at 1-800-999-0853 and they can assist you if you tell them what you want to do.
I'm trying to build an engine for towing using the clevite/melling towing cam that mad dog racing is pushing on ebay. The intake lift isn't as high as on a 4x4 extreme cam, but the exhaust lift is good. Power is supposed to be from Idle to 4400 RPM's. I don't think I should have to go over 4000 RPM's as in 3rd gear and 3.55's 4000 rpms pulls 10,000 lb. up most hills doing 60 mph. If you REALLY, REALLY want pulling power, try stroking it with a roller cam conversion, roller rockers and mild porting or aluminum edelbrock heads. Probably have to go away from the RV cam that I mentioned because of the mild intake lift, but I can't say that for sure. A mild intake lift would sure cause some swirl effect in the intake track.