The six speed gearbox will make a heck of a difference to fuel economy. I did a long ride (5000km) with a mate of mine not long back. he was on a 2007 softail custom. 96ci and a six speed box. He consistently flogged me on fuel consumption. I get about 220km to reserve for 14 litres of juice. The Harley would only use about 11 litres. I could not beleive it at the time, but more pony's means less throttle and the six speed means lower revs to cover the same distance. I would expect the same from the Tbird.
