The '61 would be ifs, so there won't be a clearance issue on the steering. I've put 32/11.50/15s on a '70 (similar front end) with no rubbing issues.
BTW, I have 30/9.50/15s on mine ('55), they don't rub at all. Must be the 1" extra width of the 265/70/15. What wheels are you running? I know that some aftermarket wheels, especially if you get the 7" width, use a Japanese truck backspace, and will rub even with a 235/75/15 on the AD/TF trucks.