One of the options on the old Excursions came on the 350 chassis as a dually with the 410 gears. Tow Monster! Friend had one, HATED to park it at any store! His duals were wider than most white lines in the spaces! Rare, but they are out there. Turning radius of a barge! Another option, get the cut-away 450 or 550 short bus chassis conversions. Those can be had used with low mileage quite reasonably, and can be set up to tow. May have to get a frame shop involved, but some come already equipped to tow.
1987 Starcraft Nova tent trailer, purch. '87, sold 8.14
2013 Crusader 290RLT bought new, 8.14 lotsa mods!
2001 Ford F-250 7.3
Loving wife, R.I.P., 6/6/19
and Mason the always dirty dog! R.I.P, 2/19