50GMC253: I think you'd have a problem. I'm running 215-75-R15 on my '53 and the spare fits into the dimple perfectly. A 225-75-16 would be 1.59 inches larger diameter (or about .79 inches radius) than my spare and .4 inches wider from sidewall to sidewall. Even though the fender dimple is wider toward the outside than it is closer to the bed side, I think it would be a tight fit, and rather than the spare fitting tight to the carrier plate and not rubbing on the fender, I think your size tire would touch and rub. You might be able to put some washers or some kind of shim plate over the bolts between the wheel and the carrier bracket to make the spare sit further out.