It is the Long Bed campers with storage boxes you have to be worried about. This appears to be an 8' camper so putting it on your short bed would not be a problem. It appears to be pretty old And 3400 bucks is a pretty high price especially if the furnace is broken. The furnace is somerthing you will for sure want when out in the desert. I would pass on it save a little more and for 5k you can get a much newer short bed specific pop up, you can use for a few years and if you keep it nice can sell for 5k when you are done with it.
Nolan