42 3/4 ton is 6 lug correct? You sould be able to swap that one out with the 55-62 1/2 ton center section. That rear will have c clipped axles. 3.90 gears should put you where you want to be, but there is the option of 3.38 available.
Sorry for the confusion. 46 rears are the full floating type. 42 rears are more or less a modified 1/2 ton that has an open driveshaft instead of torquetube. Unless your truck has already been modified by a previous owner.
