The sierra has had some changes to it, I'll make a thread for it soon. I had 35's on it, but its back to the factory 31's for now. In late summer im planning for a rancho 4" lift and 34's. It has 17" xd addicts now as well. Only other add-on is a set of rigid industries dually amber lights set in the factory bumper.
-Hammerg26, I guess im confused on your question. I put my tune on the tahoe a about 70k miles no issue. However it was a "mild" race tune so it did not put a ton of stress on the tranny if I decided to drive it nicely haha.
As far as the rust is concered, you can always sand surface rust and paint it, just depends how severe it is.
(tornado clean up, dont have many pics with the 35's)