Howdy Back Ron:
It's easy to tell a LoM from a later style distributor. When you take off the cap you will see two small advance return springs right on top. On the later style with centrifugal advance, the springs are under the point plate.
With a 5200 you will like a later style distributor for vacuum as well as mechanical advance.
YOur problem sounds like more then a carb distributor mismatch.
Adios, David