Dayton hubs became rather standard in the 1970's. Before that Erie, Gunite, Webb and Dayton had their own sizes and you just have to match them. This is what has become pretty much the industry standard for the last 50 years.

https://www.anythingtruck.com/product/130-M3.html

On vehicles made before the 1970's there was no standard. If the axle you are using has disc brakes, it would be less than 25 years old and uses the industry standard now.