More 424 troubles.

Well, this thing still won't hit a lick.

Backstory is, I was driving the tractor when it cut off. Did some checking, found no spark from the coil. Replaced points, condenser, cap, and rotor. Installed freshly charged battery, turned key on, AMP light came on. Hit the starter button, the solenoid clicked like the battery was dead. When I released the start button, the amp light went out. Found the two wires that go into the one connector on the starter solenoid broken. Repaired that, same problem.

I took the starter and has it tested, it operates on the test bench but smokes. Reinstalled it on the tractor, but now when I turn the key on nothing happens. I hooked my meter up to the battery, it has 12.7 volts with the key off, but drops to 0 volts when I turn the key on. That makes me think something, somewhere, is shorting out when I tun the key on. The wire from the key switch to the starter solenoid is okay (checked with an ohm meter for continuity to the frame), and the wire from the key switch to the black box under the left side of the dash is okay. I think this box might be my issue. With the key off, the top wire has 12 volts, and the other two wires have none. With the key on, it's exactly the same. Since one wire from the key goes to this box, shouldn't turning they key on cause something to happen?

Any help would be great! Thanks.

This is easy (or not) if the battery voltage (tested from the battery's terminals, not the cable ends, this means touching the lead round terminals themselves) goes to zero when the battery gets the key turned on, it is the battery at fault. A charged battery will hold more than 6volts when dead shorted with a heavy cable from pole to pole!!!
thus if it goes to zero it is an internal open in the battery. Case closed.
If you measured at the cable terminals the connection to the battery is bad on one or the other of them.
Smoking starter motors are in need of repair. Even if it turns on the bench, it will be unable to put out the Horsepower to crank the engine. Smoke on the bench is an indication of a dragging armature (or oil on the brushes/commutator) which need repair. Tell us more JimN