Have you ever mentally dressed yourself when packing for a trip. Starting at your feet with shoes, socks, pants, underwear, etc. Try this technique when shopping coaches. It requires that you be left alone for awhile and not hounded by a salesman. While in the coach, walk through all of your activities, from driving the coach with the slides in, sitting on the toilet with the door closed, standing in the shower to loading the refer when the slides are in. Once done inside, open the storage bays and see where all your stuff will go.
In the time frame that you're looking, the ISL 400-425 was on the market and is probably one of the best motor home engines ever made. Obviously, there are larger and smaller, but the ISL is the most popular. You'll also need to make sure that it has at least an Allison 3000 transmission. Anything smaller will be limiting.