In most cases, Honda carburetors are slightly different on the same core engine due to application and/or emissions requirements. For example, a GX120 used on certain construction equipment might require a different jet to tune the engine's power/torque to best fit that equipment. Or, a GX120 engine used in a particular emission family may require a different internal parts or settings to meet emissions regulations.
To make sure you get the correct carb, let's first see what Honda says is the right one for your engine. On the side of the block is the engine serial number; if you'll share that with me, I can look up which carb(s) are approved for that unique engine.
The serial number will be in the format
GXXX-1234567 or
GXXXX-1234567.