spare

Remember, the original Valiant/Dart tire/wheel was a 6.50x13 on a 4.5" rim.
They sat flush with trunk floor.
Bigger tires and rims sorta muck up the fit and they did stick up above the trunk floor.

If you look here, you will see the outline of the tire poking above the trunk floor on a 73..

http://www.hamtramck-historical.com/...3_Dart0017.jpg