doesn't look like there's any cylinder scoring so I doubt there would be much soot on the exhaust.

To take full advantage of a 4.0 setup, you will need head work. Yes, LNE says it all bolts in, and they are correct, I built mine to 4.0 and had minimal head work done to the 3.6 heads and it runs great but there is some hidden power there that I could get with some head work.

 

Curious if you had sent your oil in for analysis prior to doing this work, many on RL frequently say they send in samples to be analyzed, or did you feel it was already so far gone?