THat is a lot of smoke so pulling a lot of oil from somewhere. Does the engine have a PCV system in place? If so did something get disconnected or connected differently that would result in the crankcase being tied into the intake system? Given that it was not smoking originally (if I recall correctly) it is probably something simple rather than the engine being worn out.
I agree with Otto about a leakdown test but with that much oil being sucked into the cylinders spark plug condition will help sort out if its one or all of the cylinders.
