Jack placement on a 70 swinger

There should be a metal loop attached to the floorpan for the lugwrench to loop thru. The open hook part of the spring attaches to the jack, the lug wrench is threaded thru the closed loop of the spring before going thru the loop welded in the floorpan. Then you crank the jack lever to put a bit of tension on the spring to hold the jack mast in place. There is also a welded in bracket on the RH rear quarter outer fender well thats clearly shown in the pic of tge purple swinger thats a U shape. This locates the FWD end of the jack mast.

The lug wrench slides thru this welded loop that holds the spring with pointed end facing forward. The curved end with the socket end fits in the slot on the jack mast rear mounting bracket back by the taillight facing socket end up.

The lug wrench must be installed before putting the jack mast in. As the jack mast sits on top of the lug wrench in the rear mounting bracket

If your loop is missing, and the spring is missing, these parts are now avail as inexpensive repops as they were also the same parts used in B body cars thru 1970.

I believe All A body cars from 67 to 76 had their jacks stowed this way.

Hope this helps.
Matt