loaded pic to my avatar or send me an email actionpaintball at yahoo. What engine do you have?

Does this one have a battery disconnect switch? If it does, and it switches two battery+ cables and two + wires, I have seen a bad switch cause poor charging. Put a voltmeter across battery and move the switch around slightly to see if volts go up. Trucks that are left outside a lot get this.

There also is a 50 amp blade fuse for charging on some models. It's located near the valve cover, front.

Also make sure you have a good alt ground and engine ground.

someone at one time has changed the alternator and did not wire it correctly. they have one wire going from alternator straight to positive post of the battery