440 duster smokes sometimes???

it's great that you have joined the ranks of "big block darts" congratulations! back to your used engine, gaskets shrink when they get old, so replacing them all will most likely end the problems if it's engine oil. replacing valve cover, intake, carb, oil pan and exhaust if there is a ticking sound is always a great idea with a used motor anyway. a new pcv is another good idea.