Sounds like you got raked over the coals on the genny rebuild.. Here you can take in a genny that needs the commy turned, needs new field shoes and brush holders + brushes, bushings and bearing, new vr, and a harness. the harness ( reproduction) run 15$.. vr's 40$ for a good one.. 30 bucks for a cheapy and the total genny rebuild is about 80$.. new/reman genny can be had for 100-120.. even from napa..
I think I'd not use theat repair service again.. they must have kids in college.

The issue with the 1 wire jobs isn't reliability.. it is with rpm to excite. The basic internals of electrical generation are identical.. it's the vr module that is different.

I'm not fond of starting my antique equipment and then jazzing the throttle up to the 1800 rpm that many 1 wire jobs need to self excite. Heck.. I've seen old letter series JD's that can't use the 1 wire jobs because they don't turn enough rpms to make them excite... A 3 wire job will excite and charge at 500 rpm.. idle speed. Course you could always just start your tractor.. let it wqrm up.. then expect the alt to self excite when at 'working rpm' but the whole in that comes when you need to run lamps on the farm while warming up.. or if the battery was dead and you get a jump... and then need juice to keep the points going.. Most restoresrs I know just can't get over the 1800 rpm on a bone cold engine.. on
the other hand, most of the shade tree mechanic 12v conversions I've worked on, the 'mechanic' simply used the 1 wire job because it was 'easy' to hook up. That would scare me... knowing that my mechanic couldn't hook up a 2" jumper wire, and another wire to a toggle switch off the ignition, or off an accy terminal on a non oem automotive ignition switch.

Just like everything in life.. it's your engine.. you are allowed to treat it however you like... I prefer to start mine.. let them idle and warm up, and charge, and not try to throw a rod trying to wake up the 'dumbed down' alternator when a great alternative was literally 2 wire hookups different...

Soundguy