The mount was constructed 50 years ago by a heavy engineering co., and this is the 5th iteration of the drive system, reusing parts from the 3rd iteration.
The OTA is a steel frame of Brobdignagian proportions (500kg) with a 600mm f4.5 primary used at Newtonian.
A quick google on my name+observatory will reveal all, but as I replied to another poster, this is an individual project at present.
I will be considering TB6600 (Generic) driver blocks to run the stepper. Just that they are widely available and not too expensive.
OnStep should be perfectly good at running a radio telescope!!
Regards, James Albinson