Denford Mirac conversion help

[m_c]

Support for turn is quite limited from most motion controllers, as it is a fairly small part of the market, so you really need to check on specifics for anything you're considering.
.
Mach 3 turn works ok, but has a couple issues. CSS doesn't work correctly. Threading depends on what motion controller you use.
Mach 4 turn is gradually getting there, but there seems to be far more people posting with problems, rather than people running it successfully.
Suitable motion controllers would be CS-labs, Warp9 Smoothstepper, PoKeys something or other (can't remember the name of their motion controller!). Other options for Mach 3 are a Dynomotion KFlop, or UCNC, although I'm not sure how well UCNC supports turn, so you'd need to research that. As well as working with Mach 3, both UCNC and Dynomotion have their own control software (I use Dynomotion's KMotionCNC on my lathe, and although being a pretty basic interface, it just does the job without any issues, which is far more than can be said for Mach 3 :-/ )
.
LinuxCNC is another option, which would most likely need some MESA boards.
.
There are a few other options, but I can't think of them just now (PlanetCNC?).
The big questions are, how much are you willing to spend, and how good are you at configuring/programming?
You also need to decide on things like, servos or steppers, do you want to run higher voltage (12-24V) controls to help avoid interference problems, how much in/out do you need,
All those will have a bearing on what will be the better options for you.