Tim is right an eight volt battery will work without any modifications. the stock 6 volt generator should kept it at about 7.5 volts if you turn it up to max. I still use an eight volt battery on my six volt tractors. We also used to put an eight volt battery in cars when they were wore out and needed to spin faster to start. It made a major difference in flathead fords starting. Eight volt batteries are available from Tractor supply stores plus many other places.
Been there, Done that, Hope to live long enough to do it again.
Big Bill
I.I.# 4698
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