... im still going to go with cb500. it appears to have stock handlebar controls, and i think turning off the headlight died with the 500, ...
Not so. Headlight switch continued through the 76 550K models. Then eliminated for the K model 77-78.
The Cb550F model never did have a headlight switch for all the years 75-77.
This info is for US models.
In Europe there was a Cb500 K3, that the US never saw, with the new style clutch and trans. The shop manual shows several wire diagrams (and switchology) for various countries among Europe.
As this bike was imported from another country, only the serial numbers (or very detailed pictures) are going to explain what size motor it was when first sold. And even then, who's to say the internal bits are still stock?
Further, switches can be swapped among bikes. And a racer would want the option of turning off the headlight to add that wattage back to the drive wheel. Might just make a 0.01 second advantage.
Or, it might keep the battery from running down while doing maintenance in the pits.
I'm assuming it is/was a real racer, or a copy of one, of course. There are a lot of unknowns with this vehicle.
Cheers,