The mixture screw only works at idle, to change off-idle mixture you will need to re-jet.
I would get some miles on it before worrying to much. It could be loaded up for all the tuning you have been doing. Get a HEI or new points distributor, get it timed where it doesn't ping under a medium load (6-10 degree) then get it out on the highway. A good 10 mile drive will clean out a lot crud and dry out the plugs. If it still smokes, we can go from there. Joe

1937 Chevrolet Inline-powered Streetrod