Don't think getting 3.42 R&P for that dually 14 bolt/10.5 is a problem. There are 2 carrier sizes - catalogs list the ratio break - if it happened to originally have 4.56:1, that carrier won't fit the 3.42 or 3.73 ring gears - think the break is 4.10, 3.73, & 3.42 is the smaller carrier, then...