The GMC CCKW

I am looking for a CCKW late model ZENITH carburetor, rebuilt carb or kit, for the later style carburetor that has the square flange on top
for bolting on the air cleaner.

the last time I checked, these were very hard to deal with.

Any help or advise would be appreciated. I have two CCKW's and they both have this style carb on them.

Thanks