Hey Dave. First off, you are going to need a low RPM cam for what you want. You have a big, heavy truck that needs all it can get down low from the 5.3L.

I would say something in the 212/216 .542/.547 116 LSA would work well.

The cam swap is pretty simple. There are some threads about this, so use the Search tab and see what you get. If not, send me a Private Message and we can discuss.