Agreed, it is the rotational mass that you are adding that robs power. I am guessing you have a 3.8L since you have 5.13 but along with that Ripp, you are ahead of the game when trying to push 37's on a daily. I doubt it will be a huge degradation.
I also wouldn't put KM2's. They run smaller than most other tires and do poorly in really wet and snow conditions as they have no siping. Just my .02
PM me for a quote or for advice
Authorized dealer: Ripp Mods | Expedition One | ACE Engineering and Fab | Rotopax | All Pro Off-road | JCR Off-road