You don't even need the distributer cap on to set the dwell, just hook the meter up and spin the starter. Dwell is just the number of degrees the points are closed to get the right coil saturation. Pull the rotor off so it doesn't crash into your screwdriver and adjust the points for the desired dwell while the engines spinning over. Takes maybe 20 seconds. GM's and Chryslers didn't give much problem by setting the point gap with a feeler guage, not so Ford; the gap often didn't correspond with the dwell reading--especially on one with some wear.

Evan