a standard#10 won’t work. the alignment screw has a special head that allows it to push or pull the alignment ring. it has a double head, the alignment ring fits in between the heads.
Another idea: Take two 10-24 nuts and screw them onto a 10-24 screw so they tighten up against each other. Then clamp the "bolt" into your hand drill or drill press and file them both to desired dia.
This is where a cheap imported "mini-lathe" would come in handy. I have never regretted getting mine. With a 7" swing and a 14" capacity, it's really not a "mini" at all as far as my needs are concerned.
Many good reviews for this lathe.
The HP is .47. Can you take a decent cut on CS with this motor?
I think I have a couple of junk '50 Ford headlight buckets up at my shop. I'll check them today. They used the same headlights as a '40, so maybe....