Something like that, but mine does not go into the alternator (AC) lines. You put it in line with your (rectified) 12V DC feed, whether switched or permanent. Additionally, the one I have is lower current (20A) and it is built in a can, which has a third lead connected to the choke core and the shielding to provide a Faraday cage for any residual field leakage.

One of the few remaining Mk1 owners... #00015