What year truck? The ADs are narrower by something like 4 inches.
It also depends on how heavy you want it to be. A lot of cars have a rear end that is an appropriate width, but too light duty for a ton truck.
If you have the narrower truck, you may end up either looking for some reverse offset wheels or narrowing a rear end if you go to something more modern. Best thing you can do is a lot of measuring before buying anything. Chances are good you will have some fabrication involved in adapting a different rear end onto your existing suspension and driveshaft. (I'm assuming that on a 3800 you have a driveshaft rather than a torque tube.)
Couple other thoughts...
Have you looked into re-gearing the rear end you have? Are there any parts available to take it to a 3.73 or 3.55? If you can re-gear the existing you avoid all the fabrication of adapting something else.
Have you looked into an overdrive unit? Either a 5spd OD trans or a separate OD to sit behind the existing trans...
My '47 tonner (panel) is a dually, and a PO swapped a 1988 Dana 73 dually axle into it. I haven't done any measuring to compare to the original specs, but it sits under there nicely and does not protrude past the fenders at all.
