Well, pull out the distributor and take it to a shop that has a distributor testor. They will have the specs and can adjust the mechanical and vacuum advance, check for lobe wear, reset the cam angle, and check spring tension.
While its out check the wire leads as they may be broken off inside the wire insulation. Your block "may" also have a distributor bushing to support the lower end of the distributor. It may be worn.
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Stuck in the 50's
1951 Ply Concord truck
1954 Nash Rambler 2 dr
http://www.picturetrail.com/elplymino
