Valve seal are likely dried up. Have you had it out on the road and run up pretty hard, it might help loosen rings if they are stuck or not seated. Give it a good 50 or 60 mile hard run, if it still smokes, pull the plugs and see if one or more are different from the rest. Also, check and see where the PCV valve is hooked up and if there is a baffle in the valve cover, it could be sucking oil, the line into the carburetor will be oily.

1937 Chevrolet Inline-powered Streetrod