As ProMax already allows email input into the system, scrub email address against most common social networks and allow a connection request opportunity.
Create a series of tabs "streams" to integrate the most popular social platforms. Facebook, Twitter, LinkedIn. Instagram to start. Create the tabs across the note area so that you could click through social integration/communication.
Potential to integrate social messaging/ FB messenger API?
As far as I know, there are no opt-in/opt-out rules regarding social media as there are for texting, so this would allow another channel for messaging. (Make sure GDPR compliance on the dealer website, otherwise should be possible.)