Nice truck!
Overdrive is for the trans...any H&S dealer can get you the unlock code. I think it's a couple hundred bucks for the unlock. I've got it on mine and love it! Nice to go thru town and not be in 6th gear with the tc locked!!
I can't remember how to tell what tune you have!!! Been awhile since I looked. H&S website is very helpful, since I can't remember!