A "B" distributor will not work with an original Pop Out Switch. You will need a simple "off-on" switch.
Run a wire from the terminal on the outside of the "B" distributor to one terminal of the Ignition Switch. The wire that originally attached to the Pop-Out switch goes to the other terminal on the "Off-On" ignition switch. All the other wiring is the same as stock Model A.
Chris W.