With the low compression that engine has, you have to be way advanced for it to be pinging. I am betting on one tooth off. None of the other solutions have changed from when it was last run. The internals in distributor won't change just from painting it. Use a wood rod down the spark plug hole, and just watch it. The timing marks will line up and will be close enough for distributor alignment.
Just remember, it was running OK before the changes, and the only change you made to timing was with the distributor location, points and plug wires, so start there.
Joe
