took battery to battery dealer and it checked -12v. I checked the fuse box and the 4 fuses looked fine. looked at the wiring diagram and it may have a blown fusible link. Nearest Massey dealer is close to 100 mi. Going to try and go online and see if i can find a part # for the link.
Does your tractor employ an alternator or generator, if it has an alternator There is a possibility that it is damaged due to the fact that many alternators have the diodes tied directly to the alternators battery post, reverse biasing them can put them in avalanche current this can short the diodes internal junction, so that when you do get it to start the alternator will put out AC current instead of just dc.
It can also damage the internal or external regulator...It is possible that nothing was damaged especially since it took out a fusible link and did so quickly, does the alternator have a burned smell if so I would have it tested before running the tractor.. If you get the fusible link fixed and decide to try it as is and when hooking up the new battery it wants to arc more than a little when connecting it, then its probably the alternator...
Oh when they replace the battery I would have them hook up a volt meter before you leave the store, these batteries are built in lots, so if one is bad it is possible the whole lot is also reverse charged..
one more thought- some tractor makers put the fusible links at the main key switch connection, the wire will be bulged and most likely shrink tubing covered, with no battery hooked up using a couple needles you can check the continuity at each end of the fusible link with an OHM meter, IIRC the most likely place for the main fusible link for battery main power would be as above or at the starter main 12 volt wire there is probably another smaller gauge wire terminated with the large one usually to the back of the solenoid , the fusible link could be at this point, of the smaller wire going to the key switch... I do not have a schematic for a Massey so this is based on some basics.. sounds like you read the schematic so let me apologize in advance if you already Know where and how to test the fusible link, hope you get it up and running soon.