John,
Congratulations....If you are going to go with 12 volts eventually, you could buy a internally resisted 12 volt coil now, stick it on and be done with the ignition end of the swap.
If you have the proper sized battery cables, clean connections and a fully charged battery, the truck should start the same on 6 volts as it does on 12 volts.
If you go the 12 volt route, with the coil done, your only other concerns would be the charging system and lamps..maybe the heater motor and fuel gauge.
Lots of these trucks are still 6 volt and work great.
Stuart
