"If you like your fan, you can keep your fan.". Ha! You can keep your fan Tommy Gun. Technology will pass you by with advances, and so will somebody with an electric fan! I respect your desire if to keep the truck original, but if it is function you are chasing, then a switched fan is the only way. I can't think of a single road application that uses a direct drive fan anymore. Even a full semi-tractor-trailer truck with a 15L ISX or DD16 rated to pull way over 40,000lbs load uses at least an on-demand air actuated clutched fan, which is setup as fail-safe to be direct drive (requires air pressure to free-spin, 0psi=direct drive lockup).
Your belts are squealing and you are wondering why your thermostat can't hold rated temp, but after we changed mine last night, it held rated temp just fine, including a freeway drive at 65mph, with no winter front cover. I'd go dollars to donuts that a large part of that is your direct drive fan vs my clutched fan. I could engage mine solid, or you take yours off, and do 2 back-to-back tests, and let the data talk.
Rusty has a point on complex systems, especially low volume electronics like buses, but of simplistic or high volume mass produced systems, I have yet to see a failed one in the past several decades. When people say "They just don't make em' like they used to.", I am immediately following them with "Thank goodness", as when was the last time your car stalled backing out of the driveway? You probably don't remember the days of stuffing a pencil down a carb to keep the choke open after it flooded out during a start attempt.
If I call you that I'm overheated on the side of the road, I'll gladly print and eat this page. Though it is not what I would do, I respect your choice and would help you support it if need be, and you know that. How is that modern square wire alternator working on your Jeep I picked out? Kind of boring putting out 160A, and 90A at idle alone huh? Maybe that is too advanced and we should take it off and put an old Motorola 25 amp DC generator with external point style regulator box on your Jeep? I think some of those have a tach drive cable, so you should probably switch over to that also and you can watch it bounce around.
As somebody that designs and builds systems, I stand firm on this one. Keep your direct drive fans, and we'll drink beer together, but the only time you'd see me with a direct drive fan is if somebody throws one in my casket just before they close it.
Thanks for all the help last night, I could not have done 2/3 of what we got done without ya' bro.