We had a 2004 Workhorse chassis with the 8.1 engine. It was a beast and had power to spare. It even got decent gas mileage in a 32' Terra. The brakes on it sucked and you had to use two feet to stop it. We sold it a year later.
You've got a tough decision, but you could probably eliminate the older Ford 2 valve engine and concentrate on the Chevy 8.1 or newer Ford.
"Kikerdogs" listed all of the major issues I've seen with the Workhorse chassis, but if "Daveinet" is correct, a 2007 with the 8.1 would be a nice chassis. I know the later Workhorse chassis got straightened out and then they stopped making them. Tough choice to make.
