Instead of relying on the wheel configuration of cabbing machine manufacturers, you can put whatever wheels you want on an arbor. Arbors are also great for preforming faceting material.
Model 400 Heavy Duty and Model 592 Vari-Speed
Covington makes two high quality grinder-polishers that will accept two 6", 8" or 10" wheels. The Heavy Duty Grinder Polisher is a single speed unit and the Vari-Speed Grinder-Polisher has continuous speed which ranges from 800 to 1725 RPM. The variable speed allows for standard grinding speeds and lower speeds for easier stone polishing.
For complete Grinder/Polishers with wheels & motor check out the
Covington Model 752 and Model 754.