The F-53 Chassis is the one that had the spark plug issues, it seems there were not enough threads in the head and the spark plug only had like 2 or 3 threads to hold.
The no dash air is a very common problem with the F-53 chassis too, on mine the metering device was bad, not a hard fix but you have to open the system to replace it, that means pulling a deep vacuum before adding Freon. Most of the folks I know choose to run the generator and the AC unit on the roof instead of the dash air. Better cooling, more even, and cools the entire coach instead of just the drivers area.
Another common problem with the F-53 chassis is they ride like a truck. At least mine did. Even after new shocks, new tires, etc it was still a dog rough ride.
As far as dependability though, the V-10 is hard to beat. But that goes for a lot of other engines too. You will wear out the coach long before you ever wear out an engine.
Just my .02 worth.
Good Luck
