Mike - Thank you! This sounds like what I need. I'll spend some time with the Import Toolkit to get things set up.
Peter - We currently have data in a custom table like you describe but we're running into some limitations in what we can do with how we display it on the site and in search among other things, so bringing the data into pages more of our current editors can easily manage provides us with advantages.
Brendan - This is our plan for the important data being brought over from the custom table, using specific page fields to keep the precise data into needed formats, but then introducing other elements into the page for editors on top of that.
Thanks to everyone for the help!