If you want the dizzy to run at full power you should run the wire that goes to the dizzy From the under the dash to the switch pin on a relay and run a good 12 volt supply from the battery and then run a big wire from the relay to the dizzy. Mount the relay on the fire wall behind the Dizzy
Most 12 volts dizzy's will run on 9 volts but you will never get the spark you need.
H series start on 12 and then drop back to 7-8 /9 to run.