Ok Its a GF1 I restored and put a motor on one about 9 months ago. It needs a single phase 1/3 horse power motor and a speed range through a 3 step pulley of 300 to 1400 RPM I did this by running a pully to a bearing pulley to the machine, ie not direct motor to machine.
Worked very good and is a lot quieter than a sewing machine motor that will need new brushes and the speed control always playing up.
Power is an issue also small motors lack torque which is a big problem for larger stones and especially tables. You need a bit of aluminium plate bar to machine pulley's and some bearings and shafts.For an old machine its one of there better ones. They still fetch $1000 plus or minus on EBAY.I have a GF2 the next generation to this and wouldn't swap it for a new GF4. Not that's there anything wrong with the new GF4.
Single phase motor is mounted by the four retaining rods thru the frame of the motor and is mounted pulley down, so a reversible directiom motor is required. An old GMF or like is perfect and about $50 bucks on Ebay. Good luck with it all.