All intakes were cast to accept the re-designed electrically assisted divorced choke assembly beginning in the ’73 model year for passenger cars. The FSMs from ’73 on have a complete description of its function. The divorced chokes from previous years will not directly fit the ’73 and on manifolds. There were a few truck applications early on that were designed to fit the new choke wells that did not have the heating element or control. The intent was to get the choke off (spring relaxed) quicker than engine heat only could (emissions). The purpose of the choke control was to cut-off current, close to 2 amps, to the heating element after the engine was fully warm and assisted heating was no longer needed.
There were several versions of the choke control, the early design suffered from burned internal contacts fairly quickly, as mentioned. Later in the seventies there was a solid-state version.