If you have an ML7 it should have graduations on the tailstock barrel to show how far it has traveled. A bit coarse, but you can also use the handwheel. One turn, from memory, moves the barrel 1/8", so half a turn is 1/16" and quarter of a turn is 1/32" and one eighth is 1/64", or .015". It's rare to need more accuracy than that when drilling a hole. In a case where more accuracy is needed, though, you would be best to rough drill first then bore the hole to final size, using boring bar mounted to the cross slide.
I wouldn't even consider selling your ML7 just to get a chinese lathe with a DRO, providing your Myfrod is in good condition. Stick with what you've got and learn all the old time ways of doing things. Get all the books by LH Sparey, Ian Bradley etc etc and really learn how to get the best from these old machines. Remember, Spitfires and Rolls Royce Merlins etc etc were all made without DROs.
That said, budget tailstock DROs have been made from cheap digital vernier calipers before today and are said to work well. In the days of yore, a six-inch ruler was substituted, with a pointer on the tailstock. Accurate to within 1/64" again.
Edited By Hopper on 18/01/2018 12:04:18
Edited By Hopper on 18/01/2018 12:05:45