largest tires on stock 68 dart

Awhile back someone said 275/60R15 on their Valiant ('69?) with the 3/4" spring relocation kit. Do a quick search. Valiant may have different wheelwell size. Not sure. Plus that involves moving the spring pads in. I have a '69 Dart I plan to stuff fat tires under, too (all around). There's a '68 Valiant at the local yard I'm going to snag some stuff from tomorrow. I'll take some measurements for comparison.