Zane, the 6 volt coil with ballast and ballast by pass has cold weather starting advantages. Many farm tractors and some cars used it.
There are several methods to accomplish that. A Ford type starter solenoid with the extra I terminal,,,,,,,,,Some saddle mount mechanical push switches had the extra terminal to send unballasted voltage to the coil when cranking,,,,,,,,,,Some used a wire to the coil which had low resistance when cold but it increased once warm for the necessary inline ballast resistance when using a 6 volt coil on a 12 volt tractor.
Sure it will work with a full true 12 volt coil no ballast needed but that lacks the advantages above. HOWEVER if the engine is in good shape, good compression, NOT an oil burner and ESPECIALLY if you have a high capacity heavy duty high CCA battery you should be fine even in cold weather.
My choice would be use a 6 volt coil a ballast and a ballast by pass in extreme cold weather