OK. these questions come up frequently. Noobs come, they have questions, people help them, they get smarter and gain experience, and then they help the noob paying the debt forward. As it was in the beginning etc.
Your question concerning a DRO for a Wells Index mill. Your is a very good mill if in decent shape and a DRO is one of the most practical and productive revisions for use on a milling machine. There are many DRO's. You can buy them in pieces or as a package. Most of the package DRO's come with mounting hardware so if you can read instructions and can drill and tap you can do a credible job of installation.
The question is how fancy? Some DRO's have advanced features you may not think necessary at first. I suggest you keep an open mind. Some of the advanced features are very handy once you get used to them. If you have the money a higher end DRO like Newall or Mitutoyo may better suit you. You will get many suggestions as other sign on and state their preferences. If money is tight there's a way to a DRO as well.
I suggest you spend several days exploring DRO sales websites like
DRO PROS Digital Readout beats Heidenhain Newall Acurite Sargon Fagor
Displays @ A Tech Authority
Can-Do Machinery Sales - Specializing in Digital Readouts - DRO's
There is so much information available making a choice is like drinking from a fire hose. Take your time, learn the terminology, the merits of the various technologies, the preferences of people who seem to know, gather information and go through it. If you spend the price of a fair used car on something you'll use for a generations a little time educating yourself on the subject is time shrewdly spent.
How to power your three phase turre mill from a single phase service? A replacment motor may not be simple. Most turret mills use a special motor with a longer than standard shaft so the pulley is propery located in the belt case. A single phase motor for a Wells Index may be rare but I'm speaking from ignorance. But why change it if you don't have to. You cvan run a three phase mtor from single phase quite easily these days and you have several alternatives to choose from.
I submit there is only one sensible choice: a variable frequency drive. You need to know the HP of the motor and whether its a dual voltage (that is can it be connected to run from 230 and 460.) The connection diagram on the motor nameplate will tell you how and the Volts stamped on the data fields will tell you what kind of juice it likes. If the motor is 1 HP or less there are models that convert 115 Volts single phase from a wall outlet to 230 three phase variable frequency. Expect to pay $100 to $200 for 2 HP or less. There are VFD's that will power a 3 HP motor or less from 230 V single phase for less than $250..
There's a source for a VFD (variabler frequenxcy drive)
Variable Frequency Drive, AC Motor Drives, Pool Pump Motors, Marathon 3 Phase Motor, Teco Westinghouse Dealer
There are other alternatives for running a three phase motor from single phase power. There is static phase converter which will run the motor but you can extract only about 40% of the available power from it.
There is Rotary phase converter which can be home made if you're talented electrically. There are many plans and discussion groups on the topic. Google rotary phase converter. These can be a bit more pricy if you buy from a reputqable maker but the factory units perform better than most home made.
There are mountains of information ot DRO's and VFD's phase converters etc in the archives of PM and other machinist's websites.
Holler if you need a push in the right direction. Beware of bloviiators spewing nonsense.
