Trying to locate a 6 volt battery for a Farmall M. Dad seems to think it is supposed to have a Group 3, I can’t find any listing for that size, is it still made? The biggest battery I can find is a Group 2. I want bigger than a Group 1 without any doubt. What are you guys using? FWIW, the height needs to be such that I can get the battery box lid back on. John Hall