Dwell readings changing?

A worn out distributer can cause poor performance and constatly changing performance. A reman'd distributer can be like dipping one of these old cars in the fountain of youth.
If you can rotate the lobe to the high spot and push the rotor button left and right changing the point gap, replace the distributer. Check them at the parts counter the same way. I have made Autozone bring in 3 before I got one acceptable.