Welcome to the wonderful whacky world of Three Wheelers Andrew, and congratulations on your purchase and to Talk Morgan. It is a great resource and dare I say, a club in itself with many like minded people to natter to.
With regard to the wishbones, I don't think there is an easy way of identifying the replacements, I couldn't see any difference when I took my car back to Malvern to have them changed, so take it into a dealer, who should know.
As far as the pedal box is concerned, the problem, which I suspect you have discovered by now, is that the back of the clutch cylinder fouls the transmission tunnel, so you cannot use the furthest set of holes, but I understand that you can get a little more length by lifting the whole pedal box up and using a spacer of some kind under it, which then overcomes the problem, it will mean a bit of fiddling around to do this though. There is very little you can easily do to give more space between the pedals though, I had just such a moment, when braking hard when a car in front decided to turn right at the last moment, and wondered why I wasn't slowing down, anyway I worked it out in time - just. Wear as narrow shoes as you can find, preferably those dinky little racing boots, and that, with experience will stop it happening.
Best of luck and much fun.
