A '52 CA should be 6V Positive ground.
As for the ground strap getting hot, it could be several things. A constant drain on the battery, a bad ground strap or even a bad connection. I would start by disconnecting the battery and see if there are sparks. Do this at the tractor frame to prevent ignition of the Hydrogen gas that the battery produces. If there are sparks when the connection is broken, start looking for the short or bad part causing it. It could be as simple as a pinched wire under some sheet metal or as difficult to find as a bad cutout or voltage regulator. Just disconnect one thing at a time until you find the culprit.
If there is no problem with a short, clean all battery connections to insure that there are no high resistance spots that will cause a hot wire. You may even have to replace the ground strap if the connections are already good. Since the ground strap is getting hot, check the negative battery cable to see if it is also getting hot. The cables should be a minimum of 1 ga. wire for 6V. This will be about the same diameter as your index finger. The 4 Ga. or smaller (larger numbers) cables for a 12V system will get very hot on a 6V tractor.
If your tractor has been converted to an alternator, it should be 12V Negative ground. All of the above still applies, but there must be a switch or "idiot light" in the circuit for the alternator to work properly and not drain the battery when the engine is not running. Check the Research & Info section in the left hand column of this page for wiring diagrams on alternator conversions. The one by Bob Melville is particularly good and easy to follow.