Yea fair enough Stu might be different with the Au?
The EB GT Autos have 3.45s, 17x8.5 rims with 245/40/17 tyres from the Factory, the "Technicians Data Guide" that comes with them shows the Auto as having the 23 teeth Speedo Drive, this was confirmed when we took the Auto out and changed to Manual (black gear) and I re-used it in the T5, with Chad manning the Quarterhorse he confirmed my Speedo to be spot on ..
Yours will still be out with that gear as you've got a larger diameter rim/tyre combo