to make it fast?
i'd say at a minimum, throw in a 6.0 cam (along with all the surrounding components housed between the intake and oil pan)

 

but for real, if you don't mind revving it up, get some lower gears & a stall (assuming an auto) to go with a 220-something cam. that seems to be a common setup that still works alright on the street.
4.8s just don't make much torque until you start adding NO2 or boost.

 

Whatever/whoever gives you the best deal.

With that limited information and your lack of searching on this topic, that is all I will give you.