1947-1972. The HO52 was the 3/4 ton version, usually found with a 4.56 ratio, though some do have 5.13 and 4.10 ratios. Ideally, what you would want is the 4.10 version from a '68-'72, which was used in 3/4 tons with the 350 and automatic transmission. Only the 3rd member needs changing if you're wanting to improve the gearing, the axle housings are the same between the 52 and 72. That way, you will keep the larger 1 ton brakes.
