Hello
I recently had to make this decison as well.
You have heard a lot of good info
Here is what I found
Coyote Motor with Lund tune
Rrunning 315 30 18 tires in rear
391 rear end
Tremec 600 with final drive .68 (NOT .64)
I chose this as I plan to drive the car and make some nice long cruises. At 80mph I am running about 2750 rpms.... with nice fuel economy.
The final gear I found was actually a .68 in my Tremec 600
See this part #
https://fordperformanceracingparts.c...tKeyField=7618
Here is a calculator!
Engine RPM Calculator
Good Luck!