if that c6 has a windsor bell pattern, that is kinda rare, they are usually big block. if it's 2.3l then it's an i4, v6 would be 2.9l, 3.0l or 4.0l that year. converting over to auto you'll either need an auto trans mainharness or modify the existing one for lockup, neutral safety switch, and reverse lights. you'll need an auto computer. you'll also need everything for the shifter inc the linkages.
v8 option w/ auto, at least shifters can be found cheap and easy to install
start here:
http://therangerstation.com/tech_lib...versions.shtml