I'm curious on opinions on the best method to do a Cummins conversion into a Super Duty if you had to buy the truck still.
1999-2004 are leaf sprung (edited, used to read to 2005)
Diesel models are International 7.3 from 1999 to 2003.5, then the 6.0 diesel after. Both are "drive by wire" meaning fully electronic including a sensor on the gas pedal. The benefit of a diesel is you have a trans that is tuned for a diesel app like a Cummins (though it still needs help via a trans controller) but you have to buy a gas pedal, and initial cost on the diesel is much higher. That said you can sell your engine for hopefully $2500-$3500 or more depending on mileage and condition of the engine.
Gas apps like the V8 and V10 work fine for the conversion according to destroked, etc.
Using a diesel app manual trans gets you the ZF 6 speed, which is awesome. I think these were available in V10 apps too??
Slightly less work on the diesel as far as draining fuel, etc.
I've also found all sorts of 6.0s cheap with blown or majorly F'd engines. I also found good posts about replacing the 6.0 head gaskets, using studs, and milling the heads, and then they are actually pretty reliable, just as good as the 7.3 supposedly...