First what motor is in it now? Second what is your goals?
now welcome to the site but your walking into a place where just about everything has already been done. A simple motor swap has been done 10,000 times over.
Since its the big daddy being a burban and being 4x4 you might consider a 6.0 just saying.
Get more specifics on your ride and your questions. Other than that you have come to the right place if you really wanna learn.