Hi Joel,
If you do not want to distort audio in any way, the best option is to use a high quality frame-rate conversion tool to convert your footage to one common frame-rate. It is best to choose a frame-rate that is your final deliverable frame-rate.
We offer high quality standards conversion/transcoding services https://isovideo.com/services.php, based on our Game-Changer Award-winning Viarte server. If you are interested in trying out our service, you could send email to keith@isovideo.com. We could run a quick test and see if it works for you.