Help me to choose the right cam

The cam your friend suggest to you would be a real POS in your engine. Those Thumpr cams are really lumpy and run really poor.
If you want a Comp cam that will run really well in your truck stay away from Thumpers. If you want a good cam for that application I would probably be looking at a 21-221-4(Single Bolt) - Xtreme Energy™ Hydraulic Flat Tappet Camshafts

HYDRAULIC − Strong torque through low end and mid-range, good idle. Hyd. Hyd. 1000 to 5200 21-221-4
Single-Bolt XE256H 256 268 212 218 .447 .455 110°

I think you would be very pleased with the bottom end power this cam will provide.

Tom