slant six..is my distributor going bad?

It looks like the cylinders that have the longest spark plug wires are the ones with the weakest spark and the ones with the shortest have the best spark. Possibly a weak coil can't get the fire down the longer wires? You've changed everything else, might try a different/new coil.

If you are putting your timing light down by the plug try putting it close as you can to the cap and see if you can pick up a flash there.

Chuck