Hi Gina:

We'll respond in more detail on your premium Support Portal. I'll open a ticket for you there with this question.

Generally you can find details about what versions of Tomcat (and other components) will work in this documentation topic, available for every release of LabKey Server. For 19.3, for example, you can find it here:
https://www.labkey.org/Documentation/Archive/19.3/wiki-page.view?name=supported

--Molly