10 ga speaks of 30 amps. That heater gets red in just a few seconds. Even at 10 amps x 12v, that's only 120 watts. Think about the typical electric soldering gun that it rated at 100w. You push the button and it takes awhile for it to start smoking, much less do any glowing.
I like the solenoid idea as the energizing current can be handled easily with most any spst momentary on, aka push button switch and 14 or 16 ga wire.
The solenoid could be placed at a convenient place and the large wire run would be shorter which is better.
I've had numerous so I get confused. I think my 2000D 4 cyl has a push button and you can hear the solenoid close but it uses a couple of glow plugs in the intake manifold....can see them from the side of the tractor below the hood.
I think my '65 3000 has a button also. Although my TS works, I don't recall tracing out the electrical ckt.
I think I had a 4100D 3 cyl once, and a '66 3 cyl D that had it in the key switch. You would turn the key to on and both warning lights would come on, turn it a tad more and they would go out.....when they went out the TS was being powered. Hold it there for about 30 seconds and roll the switch on over to start whereupon the power is still going to the TS but also to the starter. I would imagine that they have a solenoid/relay (same thing, just the term solenoid usually refers to a high current relay) too as you really don't want any high current going through the contacts of the switch......it wouldn't last any time at all.