Can someone tell me the correct battery number for my recently acquired 1973 750 Hi-Rider? I purchased what was supposed to be the correct battery from an online seller, and I bought the one that many different sellers had listed for this bike. It may be the correct battery, but it doesn't come close to filling the space provided in the battery box on the bike. I realize that not having electric start that the bike could use a considerably smaller battery than if it did have e-start. If it does use a smaller battery than the battery box size, are there some kind of spacers used to fill the unused space?