This subject gets discussed periodically. There is a Toyota Land Cruiser power steering box that's a pretty close match to the original steering column and steering gear which has been adapted to some of the straight-axle trucks. There has also been some discussion about adding an electric-assist steering column to the original steering gear, but I'm not sure anyone has worked all the bugs out of that approach.

Another method involves mounting a Saginaw power steering gear to the left front frame rail ahead of the axle and using a drag link that points rearward to the original straight axle spindle and tie rod, but some of the ones I've seen look a little Rube Goldberg in their setup. Definitely trash the rack & pinion- - - -it's deadly dangerous with a straight axle!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!