Why not contact Morryde to make sure you get the correct part?
I see you have a 2018 RV.  Was the axle replacement covered by the warranty?  What a shame that you have to do a modification because the RV had an insufficient suspension to begin with.  It seems criminal that Grand Design would build an RV with a GVWR of 7500# and a dry weight of 5860#.  By the time you add water, propane, and any accessories not included in the specs, you are down to a cargo capacity of just a few hundred pounds.  I would also worry about upgrading the tires!