Opinion: It’s in the nature of a generator, as opposed to an alternator, to have lower output at low speeds. This was a big reason cars were switched over to alternators: In some usage patterns, like short winter trips at low speeds, the generator might not keep up but an alternator would.

The same is true of your motor. Some usage, such as prolonged trolling with lights and electronics running, the generator might not keep up. For more usual zipping around it might be fine. If you just want to start the motor a few times during an afternoon no need for a generator. Often, they were optional. So it depends on how you plan to use the motor.

The generator/regulator system isn’t unreasonably complex. The main issue is the regulator. Old auto repair manuals from the 50s-60s give details on how they work and how to adjust them. I understand there are solid state replacement regulators (for old Harley-Davidson bikes?) that may work well. The multi-pin connector may also be an issue.

So there are lots of ways you can go, depending on your electrical expertise and how much you want to preserve the original configuration of the motor, and how you plan to use it.