If both are the 68-70 8.2” Buick rear,YES,you can swap the guts,but you will still need to set them up properly. The best thing to do is take a pattern of the 3:42 setup,before you remove it from the original housing,and also take not of whatbthe existing backlash is. You will need to duplicate this exactly in the other housing. This might require changing pinion shims and carrier shims to do so. The machining tolerances were not exact from housing to housing,so you can’t just pull them out of one and put them into another.
