First off pretend I dont know anything about trucks.
Guy I work with has an 04 SWB with a 4.8. Rear main leaking and trans slipping. Looks good with 184,000 miles. Should be able to buy it worth the money. Id like to go with a reliable turbo setup eventually. Questions are. Do I keep the 4.8 or find a 5.3 or 6.0 and give it a minor rebuild. BUy a turbo kit or make one? Also what is a good turbo? also what is a truck like this worth. Ive never messed with trucks much, so this is new to me

 

You can keep the 4.8, or upgrade, it really just depends how much power you want to make, reliably. Yea you can make the 4.8 do a couple glory runs at 900hp but thats not a reliable setup regardless of what the internet says. So what are your goals?

KBRacing or Trick make good kits for these trucks, I would go with one of those unless you just want to make your own. Making your own will probably be more expensive and not as good though unless you are a pro fabricator.

Turbo depends on your goals again....Borgs are popular with the truck crowd.

Depending on condition the truck may be worth 2-6k I would say.

 

These truck have gotten crazy expensive here. You can buy a 4WD Extended cab in better shape cheaper than a SWB.
Not sure on my goals, Dont even have a truck yet. However it would rarely if ever see the track, Ive got 2 cars for this. Im not a professional fabricator but can fab and tig pretty well. Thanks for the reply