I might start with the timing. Get the bb on the flywheel lined up to the pointer on the bellhousing, TDC for No. 1 cylinder. Trace the No. 1 spark plug wire to the distributor and put a silver sharpie mark on the body of the distributor directly under the center of the cap tower for No. 1 cylinder. Take the cap off and see if the rotor is pointing at your mark, or really really close to your mark. That will tell you if the distributor moved on not.
If not, I would replace the condenser. Is Jon still making up his condenser replacements? If he is you might try one of his units as opposed to the junk we are now getting over the counter.
After that, I might take a compression test.
