It has an ATS built auto in it. It has about 12K miles on the tranny. I just put 1100 miles on it yesterday towing a 22ft enclosed car trailer. I had to drive to Vancover WA and pick up cabinets for our house. I got 17.9 mpg towing the trailer down and back.
I was really happy. The only thing I have done to it since I bought it besides fluid and filter changes was install the 4in exhaust K&N intake/filter and TST power max box. I haven't turned the box up yet as I do not have my guages yet so I have been running it on "0". I did try one take off with it set to "5" out of a possible "10" setting and you could DEFINATELY feel the difference and the tires chirped between L1 and L2.
I think the 315's will fit but all I did was install them on the truck for a minute to look at because I took them off my buddies CTD w/5 1/2 in lift and they look really small on his truck.
My friend with the CTD said he changes his fuel filter about every 10K how often do you all change your fuel filters?