Why would you need anything aftermarket. In stock form that 4.7 should be more than enough for that 1st gen. The op made no reference at to building a hot rod.
X2 on the wheelers 3leaf pack works awesome! I call it "poor mans expos"
You can see the positive arch I get with them. And this is with a small load in the bed.
Kinda hard to remove. You have to pull the whole assembly off the truck and grind off the "melted" sections from the back. There's a few of them. And after that it should come off. Them you will need to plastic epoxy them back in after paint.
I've run my 5100's preloaded and I gotta say they run ROUGH! Just as rough as a revtech or toytech kit. To me it was just to get me by until I got my OME's. For free I'd say yes.
It would be cool. But it's gonna take some reinforcing. Also the 4bt is a really shaky motor, for those that don't know what it is. http://en.m.wikipedia.org/wiki/Cummins_B_Series_engine