Welcome from another Howard!
Lathes UK website has a lot of info on the Myford M type. It was invaluable when I helped a chap recommission his ML4. he had a complete set of Changewheels, but no studs, among other problems.
Changewheels from 7 Series machines will fit, being the same DP and Pressure Angle, but need to have a 3/32 hole drilled halfway through to take the Driving Pin.
If you can get / make a couple of extra 20T and a extra 60T, you can set up a train to give a fine power feed of 0.0043"/rev.
You will find that the Centre Height changed between the ML1, the ML2 and the later ML3 and ML4., also the thread on the Mandrel changed from 7/8 x 9 (7/8 BSW) through 7/8 x 12 tpi to, eventiually, 1 1/8 x 12 tpi, the same as the 7 Series..
Threads, of course will be BSW or BSF..
The dial graduations are not plain thous, because of the 12 tpi leadscrews. At least the main Leadscrew is 8 tpi!
Ensure that the 1/4 BSW Tailstock adjuster is securely locked, so that you maintain the alignment.
Good luck!.
Howard