Mini tub

73 duster
The rear end is 44 inches backing plate to backing plate
I have about 3 inches from backing plates to frame rails
Backing plate to wheel mounting face is 5 inches
Need to know back space for wheels
I have 9 inch from wheel mounting face to outside of body
I want to run a 14 inch wide tire
On a 12 wheel
So 5 inch back space?
What about to the leaf spring?