5 speed to 6 speed transmission

[Scar55]

I have a 06 SG with 5 speed trans and 88" motor. I also have a 07 Night Train with a 96" motor and 6 speed trans. There is about 4000 rpm difference at 80 mph. I was thinking about putting a 6 speed in the glide. I'm getting conflicting information about this. I have been to several dealers and other shops. Some tell me that the final out drive is the same on the 5 and 6 speed are the same. Others tell me the 6 acts as an over drive. I've been told to change the rear sprocket to a smaller one. That would be cheaper. I know it will affect my low end performance but I don't drag race so that's fine. Opinions please