Be careful with really old bus way. Prior to the mid 70s busway was often built with the bars separated from each other over their full length. Unless additional bracing was installed their SCCR was fairly low, probably below 22kA.
Starting in the 70s busway, like Westinghouse Pow-R, is often built with the insulated bars all touching each other, so very high SCCR is easy to achieve.
Didn't the Westinghouse LV busduct go to Cutler Hammer and Eaton?
This is a link to some resources for old stuff.
Data sheets, install manuals, application guides and more for understanding industrial bus duct systems from Legacy Industrial Electric LLC.
www.legacyindustrial.com