Hy Micksurfer, welcome, yes I've seen thousands of seals like that in my career, they are used when you use grease packed rear wheel bearings rather than oil bathed bearings. I came up with some other non o.e.m. numbers, but none of them would cross back to the o.e.m. number, they are just not in the interchange book any longer. the other numbers I came up with are
5904S National, which you already knew
25135 C/R, which is actually a kit which consists of one seal p/n 503702 and two gaskets p/n 450185
SS49859 is a Victor number, none of those numbers show as available at RockAuto.
If you would like to eliminate the outer seal and just use flange gaskets, simply wash all the grease out of the bearings and hub, and allow differential oil to be your lubricant. Make sure the lube level is full and then jack up each side of the rear axle and allow some lube to run down to the hub bearings, hope that helps.
