I am struggling with which direction to go with my truck, it is a 29,000 miles truck without a spot of rust. I am a tile contractor and would like to use it daily as delivery truck that doubles as marketing tool. Id like it to be able carry 6 pallets of tile safely (2000LB ea) and dependably at modern speeds. Im leaning towards a 6bt cummins powertrain. My question is what rear axle would be best so that I can run 22.5" modern wheels and commercial tires and modern brakes. Dana s110-14? s135? Im not familiar with anything bigger so any help would be appreciated. Also would like to have front end upgrades to match. This has been a difficult choice to change anything as the truck is such a survivor.