I'd probably look at a Class C (cutaway van) model with Ford running gear. The Ford 460 tended to be a tad more reliable than the GM 454 of that era, albeit not quite as peppy. There are a few Class Cs with small block engines in them, but the fuel economy isn't much better and the power is seriously lacking (especially if you're planning on towing a small car behind it for transportation while camped).
It's easier to find a dealer that will work on Class C's, since much of the running gear is essentially the same as a full-sized van. (Many dealers refuse to work on Class A's, since they tend to be too heavy for many service lifts, and the mechanicals are different from other vehicles).
No motorhome is particularly reliable, compared to an automobile. They tend to be loaded to the maximum capacity of the chassis all the time, and are prone to heat-related problems (engine or transmission overheating, vapor lock or fuel pump problems, leaking or warped exhaust manifolds, etc.). Some of these problems are fixable with aftermarket modifications, but it helps to have a good mechanic.
Most motorhomes use quite a bit of oil, due to the hard-working engine. That means that you have to watch the oil level carefully (and hopefully, the previous owner did, too).
Another downside of all motorhomes is that if something breaks down while you're traveling, your entire living space will be stuck in the repair shop. With a trailer, when the tow vehicle breaks down, you can still stay in a campground while the truck is being repaired. Finally, pickups are MUCH easier to work on. Both Class Cs and Class As have most of the engine compartment inside, making it difficult to get to.
If you have any other questions, PM me. In another life, I'm a contributing technical editor for a couple of the more popular RV magazines.