It will only go to 6x9 if it has the 105 mm lens and Unicon 105 condenser for MF. It was originally supplied with 28 + 50 mm lenses and Unicon 50 condenser; or 50 and 80 mm lenses and a Unicon 85 condenser; or 50 and 105 mm lenses with Unicon 50 and 105 condensers. Each version had appropriate cams for Autofocus of the 2 lenses. To go to 6x9 you could put in a 105 mm lens and condenser but unless the autofocus cam was designed for 105 lens you would not have autofocus. Not everyone loves autofocus, so it may not bother you; but I do.
With the 80 mm lens you can only go to 6x6 without vignetting; I just get 6x7 but centring of the negative is critical.
It's a great enlarger, built like a tank.
You should also check that the serial numbers on the lenses agree with the Serial numbers printed on the front panel and on the negative carrier, then you know that autofocus is as set up at the factory