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!