Need HELP!! on installing '40 Ford rear brake drums

I am building a 1940 Ford with a Columbia 2 speed rear-end in it. It has the stock/original rear drum brakes on it with new shoes, new wheel cylinders, turned drums with new bearings and seals installed in the hub. I cannot get the drums, with the hubs still assembled to drums, to go on the taper axle ends with the key installed in keyway. But if I removed the key, the drums/hubs will slide on. It has the original key and it has no burrs on it, have filled it smooth and clean. Is there a certain procedure to installing the drums with the key in place or a special tool that must be used to installed them, such like the tool used in the removal of the drums/hubs? Any help would be appreciated and very much needed. :confused:
Thanks,
Ronnie