Hi. I'm looking to lower the final drive ratio on a 147GTA for road racing. I understand that the 2.5L 156 gearbox and final drive ratios are lower with a FD of 3.94:1. Ideally I'm chasing a FD ratio of aroud the 4.1:1 or lower. Does anyone know of any gear sets that might allow me to achieve this?. I have also heard that the 166 2.6L sportronic FD ratio is 4.223 but I do not know if it is interchangeable into the 147GTA casing and gearset. Any feedback would be greatly appreciated. Cheers.