Wouldn't a camper that fits a short bed or long bed be alright?
I mean... the width of the camper doesn't vary that much does it?
A camper that fits "short bed OR long bed" is fine, but a camper that fits JUST a short bed requires some compromises.
The "short bed only" camper will sit back 18" from the front of the truck bed. Sure it will work, but you end up with an 18" longer rig, or you give up 18" of valuable interior space. It's been done many times of course, for example when you find a deal on a camper that's too good to pass up.