Hello jim Del,
You could try to borrow another known good distributor to verify that your distributor is good or bad, before rebuilding. Does your distributor's rotor and shaft move much when rotated by hand, indicating slop between cam and distributor gears? How about the bushings in the distributor, is the shaft wobbly or ok? If able, try rotating your engine's crankshaft clockwise and counter clockwise while watching the distributor's rotor for movement, possibly indicating slop in the timing gears. While your engine is running at idle, does it stay at a steady RPM or does it surge higher and lower RPM, following an advance and retard of timing? Let us know those answers, OK? Good Luck.