Update old Ruby/Rails app to use modern database driver.

We have a fully developed and functional Ruby and Rails app that was written in 2008 and is on a VPS server running MySQL version 5.5 that is very outdated and needs to be updated, but the Rails app is written in Ruby vs 1.8.7 (patch 374) with Rails version 1.2.1. The problem is with this old MySQL, it needs to be updated. The application is up and running fine, but efforts to upgrade to a newer version of a database have failed due to their not being a database driver for a newer version that can connect or compile to this old version of ruby (1.8.7) and it seems upgrading the ruby requires updating the rails version, which then requires some application updating. We are seeking the minimal rewrite necessary to update the app to work with a newer database driver so that database and server could be updated (the old database is breaking the ability to update the CPANEL/WHM server on the VPS)