The 300 should be an HD model, different exhaust manifold, forged crank, not a lot else different. Same "size".

The stick with the button on top is the parking/emergency brake.

PTO operated lifts use two levers. One engages the PTO to run the pump. The other operates the valve to send pressure to the ram(s), to raise the bed, and then to let that pressure off so the bed will lower.

I doubt it's a Muncie trans. Probably a Clark. Run it through the gears. Maybe it is an OD. Maybe it's a 4 speed with a 5 speed ****.

As for tonnage, an F600 is, I suppose, a "2 ton". GVWR might be around 16-17,000 lbs.

My dad had a '58 and he loaded a lot more than that on it from time to time. I think he had it licensed for 24,000. I can tell you 24,000 is way too much BTW.

Expect to have to go through the brakes, or your might be going through something else.

Good luck with it.

As for 13960 miles, add 100,000 or maybe double to that.