Steering wheel boss for aftermarket wheel

I'm after a smaller wheel in my disco. The standard one is like driving a bus it's mahoosive. I can find plenty steering wheels and bosses but how do I know which is right? I see bosses with different spline numbers but don't know which will fit.


Anyone care to shed any light? mr noisy perhaps? I know you've got one Sam but don't know if an earlier disco would be different.