[RichardJ]

To check for shaft wear, remove vacuum source (as in other post) and rev engine up-down. Dwell should not vary more than 1-2 deg at most.
To check for point plate wear, operate vacuum canister with hand vacuum pump. Again, Dwell should not vary more than 1-2 deg at most. Dwell will vary some because the point plate doesn't rotate around the same axis as the dist shaft. The point plate rotates around a pin beside the shaft. Not the best design, but works well enough.