So i contacted lmc about an rear wheel seal for my 56 f250 and he part number they show is 45-0155
It shows its 35/32 outer diameter and 1 9/16, does that make sense..i measued the old seal it looks to be about 3 .5 inch od

 

If your truck has the stock full floating rear axle, the seal will be the larger. Possibly available at NAPA. The part number should be visible on the old seal.

 

The only marking iz fordco no numbers