I'm not sure what they did in 1988, but my 1989 Ford E350, Fleetwood Jamboree, Class C had a 460 with throttle body injection, E40D transmission and a catalytic converter. It was a 27' and got about 8.5 mpg/7.5 mpg towing. The engine ran strong for the fourteen years/65000 miles that we owned it. We towed a 4500 pound boat most of time.
On my model, Ford install what could best be described as a pair of small plastic trumpets in the air cleaner air box. They were designed to force feed air at low speeds. I cut those out and improved top end performance and mileage, but lost a little low end acceleration. I'm not sure about the Class A, but the Class C had a catalytic converter that was known to plug. Ford ran the exhaust out of the engine at 3", into a 2.5" converter and then back out to a 3" exhaust. You can cut the converter ends to 3" and weld the exhaust back on. This was another performance boost and allowed the converter to run cooler.
Other than that, the drive train was solid and pulled hard in the hills.
In that year model, mine had the rubber roof which was a pain over the years. That would be my biggest concern on a coach that old.