I've been looking at this also since I have a parts truck with cruise. In the end my decision is to swap cabs due to damage on my project (not just to get cruise, LOL) so I'll have cruise without much other modification.

Here are photos of with/without cruise. As you see, the wiring is already under the hood for the cruise "servo" and the brake pressure switch.
(Note: both of these trucks are 4.9L 5-speeds.)








Of course swapping your steering wheel (or getting another column w/tilt also ...see other projects here) will be necessary. I'd have to do more research to determine if the clockspring would need to be changed or if it's already cruise equipped.