The gears in the LMC catalog are for the Dana rears per note "A". Most of the trucks of this series have the 10 bolt Eaton with the round cover. Be sure what you have before you order, and don't depend on LMC having tech support that can help you.
If you have the Eaton HO52 rear and 4.57 gears, you can do a pumpkin swap and get 4.10 gears, if you can find the pumpkin. The HO52/72 was discontinued in 72. Another option is a pumpkin swap from a 14 bolt full floater, but you have to swap the axles due to a spline change. 3.73s are an easy score that way, but you will need to find one with the same axle length.
