I've got an idea for you: Buy two trucks, one a quad or standard cab, long bed dually. The other, a Mega. Same color, of course.
Cut both frames behind the cab, then put the dually half behind the mega, and the short bed onto the quad. Swap all wheels, drivshafts, exhaust (one section) unplug wiring harness at right point, and swap brake lines, fuel lines, and you've got your mega/dually.
Zero parts cost, zero paint, just frame labor. A body shop with an alignment jig, can do this in one day.
Only problem is, the VIN of the short bed will now read dually (for insurance and taxes).
Not an issue if you keep both for yourself though. Wife can drive the shortie.