I figure it would be better to build what I wanted because I couldn’t find it cheap enough.
If you would rather switch all the drivetrain components than the cab, you must be a member of the “extra work is fun club”. I know people who have converted 2WD to 4WD, and it takes weeks of cutting, welding, fabricating, measuring, and in many cases, do-overs if you didn’t weld something in quite the right place. It’s a lot of work and requires a lot of skill. Switching the cab consists of 6 or 8 body mount bolts, unplugging the wiring bulkhead and windshield wiper motor, disconnecting the master cylinder, removing and reinstalling the cab, and hooking up what you disconnected. You will need some strong friends for a couple hours, but you would need them for the powertrain swap anyway, probably numerous times.