It's a truck, it was never meant to go fast. Just keep that in mind throughout the process.
That being said, there are quite a few things you can do to a 360/5.9 to get more performance that are WAY more cost effective and will probably give you less headache than a hemi swap.
First off, do you want to go faster over all, or do you want to get up to speed faster (top speed vs 0-60)? If it's 0-60/acceleration of the line/responsiveness you want, the easy and low cost mods that should make a noticeable difference are Tb mod, cai, exhaust and programmer (assuming you have an automatic, I think 5spd will benefit much less). That should get you started. Then you can start looking into an intake upgrade (mopar m1 or Hughes), headers, cam, possibly turbo or supercharger etc. and you would still probably come in way lower $$$$ than a Hemi swap and WAY less headache. Before you do anything, check if there is a vacuum in your crack case (pull the oil cap while the engine is running and put your hand over it). If yes, you'll need to do the plenum job before any modding to ensure your engine ifs running healthy.
If it's a better top speed you want, sell the truck and buy a charger with a 440.
