want to put a standard dually bed on my 2005 cab/chassis

its not that that you have to worry about. frame rails are different widths apart. so youll have to figure out a way to mount it. and youll have to have different height mounts because bed isnt flat on the bottom.

Pretty sure he will still have that gap between cab/bed.(or is that only with xcab/crewcab?) But yes, frame rails aren't the same width. Cab/chassis rails are narrower, as is the axle I think. There is one locally that did exactly this...rear tires tuck way inside the fenders...just looks goofy to me, but I'm OCD about that stuff.

i have the alcoa 22.5 wheels on it so they wont stick in. i can cut and weld the bed on there but i just dont like that it will have a gap. i think im just going to have to put a flat bed back on.

I know on some cab/chassis trucks there is a gap. Not sure if there is on a reg cab or not. Hopefully someone with experience will chime in here soon. A little google searching should get you the difference in widths between a chassis axle and reg DRW axle.

yea ive been doing alot of research and looks like i will be having to do alot of cutting and welding in order to not have that gap. or maybe put stacks to cover the gap?? lol

There have been several afremarket companies that made F550 pickups. Fontaine and Classic Coach were two of them. They made a fiberglass spacer that bolted on the bed to fill the gap. I have seen them for sale on ebay. Do your homework and I'm sure you can find one.