[Shane 1953 GMC]

Good Morning, I recently purchased a 53 GMC long bed. I am debating on tubing it out, but would like to stay away from that if possible. My question is, what is the widest tire I can get under the wheel wells with out having to do any cutting? It has a straight 6 with a 4 speed transmission. I was thinking it would be a tall gear but not sure without pulling it apart.. any ideas? thanks everyone in advance.