2003 jeep liberty 45rfe transmission TCM swap to a 545rfe???

Okay, I'm just curious if anyone has heard or has done this. I heard and read about the 45rfe transmission and the 545rfe transmission being exactly the same besides the programming in the TCM. I've also read and watched some videos on people changing out there TCMs in other jeeps that had 45rfes and turning them into 545rfes. Does anyone know if it's possible to do this with a 03 jeep liberty and if it would make a significant difference regarding MPG and such?

I know it has been done for fact on older Grand Cherokees and Rams. You are correct, no difference but programming. Theoretically it should be doable (TCM's aren't VIN dependent) but will you actually get any use out of the extra overdrive gear (that's all it does, gives you 5th gear)? I imagine if you spend alot of time on the highway at decent speeds then it might be worth doing.