You may be correct on the VIN designation but, I coulda swore I got that info directly from the Goerend website. Later!I thought VIN "6" or "C" was S.O. or H.O., guess it's the tranny package too. I thought the H.O. motor was only available on '03's with the NV5600 6 speed, is that wrong? The tuner won't bring a 260 hp motor up to a 305, if I am understanding you correctly. Just to clarify, are you asking if you take, lets say, a 100hp chip and add it. Now, if its on the 260, then it would yield 360. On the 305, it should yield 405, at least in theory. are you asking whether it will make the 260 up to 305, then add the 100 extra hp? Also, good tuner for the '03 would be a smarty for all around performance.