You can get conversion units from Dr. ATV aka Beatrice Cycle. The taillight bulbs in 6 volt should be available in any auto parts store. The signal lights (if you have or need them) can usually be found there also.
There is an option of using a 6 volt LED bulb for the taillamp also. They are available at
http://superbrightleds.com/other_bulbs.htm . Look under the "new 6 volt car bulbs banner. The company is pretty good to deal with. Fast shipping and all.
If you need indicator bulbs for a speedo on a ct70, those are available from Beatrice Cycle above. Their direct link is:
http://store.yahoo.com/dratv/noname157.html that page should have the conversion headlamp too.
If you get a new chinese motor, most of them are 12 volt, so the bulb issue is not a problem, except that you will need to convert the sealed beam to one with a replacable bulb, or get a whole new headlamp that is 12 volt.