the point faces have to be clean and shiny. When they sit for some years years, a film often covers them, which needs to be removed so they can make good contact again.
I would first recommend removing the point plate, checking the function of the mechanical spark advancer, lube up the point cam and then reinstall the point plate. Turn the engine over so the high spot on the point cam opens each set of points, set the gap to .012-.016", then move the backing plate until they open at the F and LF marks.
Check each contact set with a volt meter or a test light to see that each one is getting close to battery voltage.
Check them when they are open or put a piece of paper between them temporarily. When you are checking the timing with a light or meter, you should see the power go on and off when they open and close. If the light or meter stays on and the points are closed, then they are still dirty or have some grit between them.
If you have been cranking the engine over with fresh plugs and only one has been firing, then they may be fouled again.
Be sure you have a strong spark at both plugs. Check the plug caps for resistance values around 5k ohms. Unscrew them from the plug wires to check. If you are cranking it over and you see a lot of arcing on one set of points, either the condenser for that side is bad or the wires where they attach to the coils are loose at the connectors.
Check the compression to see if it is around 175 psi on both sides. Set valve adjustment to .002 on the intake and .004" on the exhaust sides.