A simpler alternative is to fit the higher 5th gear pair from another Fiat (Punto?). I've got the details and part numbers somewhere - seem to recal it raises top by about 7-8% so makes cruising on the motorway less buzzy. Works well with a remap. There's also a how-to somewhere on here. It's a pretty simple swap from what I can remember - you don't even need to remove the gearbox. Getting hold of the gears might be a challenge nowadays...