56 newbie, i know you asked for the number, i did my seals last fall and no longer have the boxes or the numbers, but the parts store i went to had the seals right behind the counter, no waiting involvled. if you have a decent parts house in your area, they will probably have a good line of seals. that number might not be as rare as you think. i went in friday night to get a pinion seal for my 55 first series friday night and it was the same story. they had it right there in store.i don't think you will have to take it apart first, just tell them the application. good luck.
