I trying to put back together a 66 Lemans A/C car that was stripped out. i bought a used box. it seems that i cant get the center diverter door to work. the wone that diverts to the into the large plastic duct that goes to the dash outlets. i noticed that the defroster door has spring return and vaccum to open. the center door does not.

would anyone have any ac parts around or an ac car to tell me where a spring would hook up to and what it would look like. better yet. have a spring. Any help is appreciated.
thanks.