I can only tell you what I have. I have a 8' bed and the rear golf seat floor board is detachable so I can still close my tailgate. So pulling a trailer with the golf cart in the bed of the truck is no problem for me. I have never owned a short bed so I don't know about that.
You can theoreticly fit it in a shortbed with the rear wheels resting on the the tailgate...but youd need to make sure you have clearance for the pop-up on turns while the tailgate is sticking out.
We have a long bed also. We do not have the folding foot rest on the back seat, so our tail gate does not quite close. Also, be sure to remove your roof and windshield if you are traveling over 45 mph and for any distance....I speak from experience...we lost a windshield!
When we had our popup and TT, we put the cart in the bed of our Tundra. It was a standard size bed and we had the tailgate down and secured it. Like Rog said earlier, make sure you have clearance with the tailgate down. We ended up getting a small trailer for it because the Tundra was so high off the ground, it made getting the cart on and off a royal PITA.