Here is a little different look at it.
As far as the chassis is concerned: A Ford V8 (460 ci) is a very good motor that was made for many many years as was the Chevy V8. Parts are readily available for the motor and tranny. A well maintained V8 will give you 200k miles without a rebuild. The tranny will give you close to the same IF well maintained. With that said there will be things that will not last 200k. Belts, hoses, water pumps, alternators, power steering pumps and so on. If you plan to buy an older RV then you need to plan to do some repair work to it. Its no different than buying an older car as far as the drivetrain is concerned.
I have owned 2 motorhomes. One with the 460 Ford V8 and one with the Ford V10. I do like the V10 better but I would not say that the difference is huge. The V10 seems to have more power and require less downshifts so that is why I like it better.
When looking to buy a used motorhome you need to break it down to 4 categories.
1: Things you need
2: Things you want
3: Quality of the coach (the stuff above the frame)
4: Chassis (the stuff between the frame rails).
Items 1,3 & 4 are the most important.
