What fits?

Often wondered this, but what size tire can you get under the back of an uncut quarter, non-relocated spring '69 Dart? The Wheel Guy(?) In Indiana (I think) had a set of small bolt pattern steelies that were 15x7 or 15x8. Can't remember. Think a 275/60/15 would fit with the right backspacing without rubbing?
I have asked a similar question before, somewhere, and got sent to Bigblockdart.com and many other places, but most talk about tubbed, mini-tubbed or trimmed lips on the quarter, springs relocated, ect. Looking for someone who stuffed as much tire under his(her) Dart without cutting...
Thanks!