will 275/60/15 fit 71 Duster ?

Here is my 71 Duster with relocated springs with 275/60/15 M&H Racemasters.
No problems with rubbing but this is all you can put there I guess.

With a 3" relocation you can get more in there. I have 295's on my Duster using the stock wheel wells. I did have to trim the outer quarter lip back almost a 1/2" though. Heck I only have a 1/2" hanger/shackle offset on mine. But 295 is as big as you can go with the stock wheel wells, to go bigger than that you'd have to mini-tub.