Non-pro diffs are 43/13 too- its best to use this version rather than the pro as the pros obviously lower your overall ratio by quite a fair bit, meaning you need a seriously small spur or huge pinion to get the correct overall ratio.
Its well worth picking up 2 or 3 pinions though to experiment with your ratios- 18, 20, 24 for example is a nice spread, and combined with several of the cheap spurs you can fine tune your ratios very... finely.
