Yeah Steve as I stated I have Gen1 Sync without navigation - NOT MFT - I have the same type of Sync you do. The problem is that Syncnyride.com & the Ford Customer Care website typically only lists the versions that you yourself are able to do the updating on. There are versions that are only available as Dealer installs. Prior to the version I have now, syncmyride.com listed me as having the latest version even though there was a later one only available by dealer install. Contact your dealer and see if they have a dealer install version of Sync to help you with Text messaging.
In addition to just having your phone synced with Sync, you have to have MAP Profile enabled in the Sync menus and message notification turned on.
1.) In SYNC, go to SYSTEM SETTINGS, ADVANCED, MAP PROFILE. Set MAP PROFILE to ON
2.) In the PHONE SETTINGS Menu in SYNC, go to MESSAGE NOTIFICATION. Set to ON
Now in the settings on your phone under bluetooth. Pick the gear icon by sync when you are synced up and make sure you have Call Audio and Media Audio checked and on.
The first time you a receive a message in the car your phone will give you a notification that SYNC is requesting text messages through Bluetooth. Make sure Always Allow is checked and hit OK on your phone.
All that has to be setup and happen in order for texting to work properly on ANY phone, not just the GS5. Now this will not fix the Sync ringtone issue where it always plays the Sync ringtone, but it will get texting working. Also, I have my Sync set to Sync Ringtone #2 and that is much less annyoing than Sync Ringtone #1.
Good luck.