Six volt to 12 volt, I know why now

[oldford]

Purchased a 32 ford and the 6 volt had been changed to a 12 volt system. I really did not want a 12 volt so I installed a 6 volt battery to see what engine would do. Engine would barely turn over. With the 12 volt it spun it like a top. So guess I will keep the 12 volt.
You guys said the starter will take the 12 volts but the bendix needs to be stronger. Can someone send me a brand and part number of one I should use. thanks