Hey RATRODKING,
On my '55 and '56 the vent pulls were mounted under the dash and to the end of the vent flap was a upright holder that mounted to the top of the vent opening and locked the cable in place so you could open and shut the flap. I wish I had a pic. but could not come up with one.
Look on the upper inside trim of the vent opening and the holes may still be where you need to mount the brkt.(driv. and pass side)
Good Luck,
mike
