From the page that was linked by Denny. Read to the bottom. And they give you the interchange info.

Info
Inner hub bearing seal for Wilwood Camaro, Nova, GM A-body kits as well as 49-56 Ford kits. Interchange with National seal number 40494S.

2.50" outside diameter
1.75" inside diameter
0.25" thick

But your measures don't match with this one.