The base of the return spring is looped through a hole on the bracket that mounts the engine end of the firewall bellcrank. This is very near where the LH head surface intersects the block - and right behind the temp sender and grounding bolt. The upper end of the spring is on a "bendable" lever arm that allows a little bit of tension adjustment. 

There are about a zillion links and levers in the Bird throttle control and trans kickdown system - hopefully your sedan isn't that complex.