The frames and cab mounts are different between the standard and extended cab vehicles.
You would at minimum have to re-position the two rear cab mounts. Then you would have the opportunity to cut the bulk-head off of one bed and about 2 feet off the other bed and make a single cab with a 10" bed (or 4" if it's a 6" bed).
Unless the extended cab PU is a 6" bed, then you'd have to put the 8" bed on it (And two front mounts). However with the difference in the frames the bed would still have to be modified as the wheel wells wouldn't be centered correctly and the tank (fuel) may have some issues to deal with.
Last edited by Warlock III; 08-11-2013 at 05:28 PM.