need tolerences 4 carb level or workaround

Got pictures?
The carburetor can be a half bubble off of plumb. But anymore that a few degrees and the float will not control the fuel level inside the float bowl correctly.
You may have to improvise a copper elbow or two, commonly used in plumbing, to get the carburetor level.

The fuel inside the float bowl will seek it's own level, or in other words, no matter what angle that carb sits, the fuel will be true and level to the ground. If you have a carpenter's bubble level you can hold it up to the side of the carb, watching the bubble to be sure it is level, and that will let you visualize where the fuel will be in relation to the carb inside the float bowl.
If I were building that bike, I would do something to get the carb more level that it is right now. It may work as it is currently, but it won't be right as far as the carb is designed to be installed. They like to sit flat and level.
You can always try to run it the way it is now and decide later if you need to correct it.
I suspect that you will have issues with it running too lean at high speeds