A semi educated guess here.....the HD-150 uses 359:1 byers gears on both axis correct? The G11 uses 359:1 gears also doesnt it? The Byers you have has the losmandy 492 stepper system already installed on it correct?
As far as I know those digital drive 492 stepper systems were setup for either the G11 or the G8.....I would venture yours is for a G11. Since both the G11 and the HD-150 use the same ratio drive gearing it stands to reason the only thing you will need to do is swap the motors and tell the gemini you have it installed on a G11 which the Gemini has all those settings in it already and is a simple one step pick option in the menu.