^^ what they said.
A 31' tire is about 18% oversize, so you should be looking to get an additional 18%, or so, reduction somewhere in the drive train. Two ways to get it are: 4.30:1 R&P gears (two sets, F&R) , or either of the two available 4.9:1 Tc's gearsets, which have about that much (16/18%) additional reduction in high range. That particular R&P ratio is kinda hard to find. A stock 1.3L should not need a heavy duty clutch, if the flywheel is properly resurfaced (both inner and outer).
