I recently bought a 1964 F100 long bed and it came with an extra short bed.What do I have to cut/modify/change to put this on? Or will it bolt right on? Also the short bed has a rotten floor. Will I be able to trim the long bed floor to fit the short bed?

 

Yeah - it would likely work and be a horrendous pain at the same time. Plus you're left with an empty space in between the cab and bed then. Maybe load a big side access tool box in there custom made? Either way to balance a load in the bed you should try to center the bed over or slightly forward of the axle. that's my best tip for stability in a work truck. If weight is shifted too far front or back you get steering strain (misalingment under heavy load) when too front or axle pickup (front end picks up off the ground (slightly if you're lucky) when you hit the gas). Either way though you will end up with extra frame and a lot of trouble. Worth it if you're chopping it short for off-roading otherwise I'd sell the short bed to buy nice stuff for the truck as it is (unless it came with a short bed and the long bed is wrong for it). I guess it comes down to a judgement call.