The key is figuring out which contacts are closed on the accelerator switch.
What is it, a multi-bank rotary switch?
Or what was known as an encoder back in that era? (PC board with different length traces laid out in a circle and a movable wiper arm with multiple brushes.
Pictures of it would be nice.
Looks like F and R are incorporated into the keyswitch.
Looks like two 18V battery packs that are connected in series for charging.
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Ironically, I've worked on similar circuits before, but not in golf carts.