I think either Ford or Workhorse chassis are fine. Our gasser was a Ford. I would definitely consider adding a Banks system. Both the Ford and Chev motors have had a history of warped exhaust manifolds. In our case to the point we had to replace a cracked head. The Banks system prevents that problem and improves performance particularly in the mountains and for towing.
2002 Tradewinds LTC Founders Ed
2004 Tundra Double Cab toad, 2007 Honda Goldwing