What size tire for back of 69 Dart GT vert?

Thanks again for the great pics!
Is there anything stamped on the rim that indicates backspacing?
Im guessing my Cragers are not as there is about 3-4" from inner tire to spring and only 1" from outer tire to fender (3/4" on one side actually).
Would be close... and I also have chrome wheel well trim that need to go on- so dont wanna have to bend fender.

New rims are not in the budget unfortunately...