My Northstar Adventurer is made for both long and short bed trucks. I have the short bed version which allows Northstar to add some outside storage in the overhang area. As Camper8251 mentioned, the important thing is the COG of the camper. Some models designed solely for long bed trucks may have their COG too far to the rear to safely carry in a short bed, even if the overhang is similar to the campers designed for both.
Now as to a short bed camper in a long bed truck, a few people here do it but I believe all have some sort of bed storage in front of the camper giving the camper a backstop so it isn't only the tie downs holding the camper back when you hit the brakes. In these cases COG is also something you have to consider, though the weight of whatever is stored in the bed in front of the camper weighs (pun intended) in that COG calculation.
An older truck with a newer camper is often a safer choice than a newer truck with an older camper. For example, GM narrowed the width of the bed opening making it so older model campers won't fit. So I'd measure tailgate opening and the width of the tub, the part of the camper that goes through the tailgate opening, is the most important. Situations like lack of clearance between the overhang and truck cab or truck bed side rails can be compensated for simply by adding 2x4's or some other spacer in the bed to lift the camper.
