Back in the day (about 50 years now) I had an ML2 driven direct from a 1450 rpm motor by flat belt onto the headstock. Absolutely dire!
I built a countershaft unit hinged at the back of the bed with motor hanging off the rear, V belt drive up to countershaft. I modified the lathe to V belt pulleys by turning the cast iron flat belt pulleys off to leave a parallel sleeve, then loctited a multi step picador pulley onto the remaining sleeve. It worked OK. I later grafted a clutch onto the countershaft which saved a lot of motor stop / starting.
If I was doing the job today, I would use Poly V belts, J section, you would only need 4 groove pulleys and they could easily be turned into the existing cast iron pulley. You will need to beg / borrow / steal another lathe to the turning though.
A little warning – my ML2 had the cross slide feed screw graduated at 80 thou., but the screw was actually 12 tpi giving 83 thou advance per turn. This caused quite a few scrappers until I worked out what was happening and made a 12.5 TPI screw and tap. In hindsight, I should have made it 20 TPI, and re-made the micrometer collar with 50 divisions.
Hope that helps.
Martin