Either the fork was built for a really tall stack height for an unusual headset (were there any in the mid-1970s though?), or it might have been replaced somewhere along the way. May be worth it to do a check of the bottom of the headlugs, to be on the safe side.

Honestly, I'd clean it up lightly and try the CR list with a straight-across trade for a similar-condition, mid-1970's Super in your frame size. Also leave it open to the option of swapping frames only. If it's the same era Super to Super, moving the components over would still be true to the donor frame.

-Kurt