First off, welcome to RamForum. Our 85mm throttle body will work well with your current mods. Do you have any plans to add a tuner or headers down the road? Aside from your daily commute to work, how else do you use the truck? Any "spirited" driving?
If you have any plans to add headers, then I would go straight to the 87mm throttle body as it will show better gains in the end. Otherwise, the 85mm is perfect. You can expect to see an increase in throttle response and about a 10-12hp gain in the mid-upper rpms. Many customers even see a slight increase in mileage on the highway.