Does anyone know what the shortest bed you can put on a reg cab f450 with 164" wheel base?

 

As short as you want, depending on your fabrication skills. Your question is going to need a little more detail. I don't think they ever came with anything but an 8' bed. Some guys have put 10' on them. A short bed will require some cut'n and chop'n.

 

I think he's referring to a chassis cab. Should be a 165" wheel base, 84" cab-to-axle. That's just a touch over 11' of frame, the fuel tank is likely behind the axle, I would suspect a pickup bed is going to be out of the question unless a guy has 2 donor beds and some awesome body work skills. As for a flatbed, most upfitters will spec a 12' bed for an 84"CA, but you could get away with something about 11', but I'm not sure who makes one that length.

 

Yes I was referring to a cab and chassis. 11 foot is what I thought but wasn't sure. Thanks

 

I'd have to measure mine (I have the same WB/CA truck as you're referring to), but as I recall, it was just over 11' to the end of the frame rails. Many flatbeds for your truck are going to be 12' and have a crashbar/rear skirt that hang past the end of the frame rail. Also, if it has a frame mounted trailer hitch, that's going to stick out past the end of the frame rails a bit as well.