the only difference between a dual field squareback and roundback is the serviceable pressed in diodes of the squareback. all other things being equal. There is no + and - on the distributor leads. either will work, (one closest to lug is labeled as + in FSM) they both end up at the 2 position plug of the electronic regulator with one tapped off to the ignition wire. Make sure you have a good ground (star washer) from the regulator case to the firewall. any dual field can work as a single if one of the fields is grounded to the case and the other goes to your old mechanical regulator, as I have been told.
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