Wow, that worked perfectly! I didn't even have to load the map into my layout.
When you choose the drop down for "Existing cached map/image service"
It prompts you to find the service, not by looking in your table of contents. I just went to All Portal, typed in 'world topo map', choose the "World Topo Base", and then I was able to adjust my details levels to 1:71!
Thanks for the help, Kelly!