I'm running 30x9.50x15s on an 8" Ralley wheel on my '55 2dn Series, which has the same fenders in the back as your '61. I have at least an inch clearance from the tread shoulder to the fender lip. I have bottomed out the suspension with no rubbing on the fender. I have seen '55-'66 Stepsides with wider tires, though not quite that tall.
Just out of curiosity, is there a reason you're wanting a tall tire?


Bill Burmeister