Trucks built after June 2004 were labeled 2004.5 trucks, 325 hp, 600 ft-lbs. 2004.5+ have four inch exhaust system. The 48RE transmission is fine as long as you run clean fluid and change the filter and adjust the bands per spec. I have owned mine for 5 years and it has been flawless, just filters and fluids. Subject of air bag recall. Above average fuel economy. Exhaust brake add is a must. More engine noise than newer diesels. Simple to access fuel and oil filters. Would prefer a crew cab over quad cab.
Can't figure where the knocks are coming from, my truck's paint shines, no rust, the leather is excellent and the dash is perfect and in one piece. I tow a 10k# fiver and the truck does fine, gets me there every time without drama or incident. Very low depreciation.