A little more info will help. Assuming this is for a 216/235/261 that's in your pickup, which currently has the pedal starter and has been converted to 12 volt. Chevy Duty shows a 12 volt conversion starter, I don't know just what it is. Does it have the same linkage for connecting as your 6 volt starter? If so, just put it in. If not, call up Chevy Duty and ask what it takes to put it in.
Before you bought the starter, I would have recommended finding someone local that rebuilds starters, if there was something wrong with the old one. They could have rebuilt it and converted it to 12 volts. If all you did was convert to 12 volts, the 6 volt starter will give years of service. But, I don't know just what your circumstances are.
