steering wheels....splines

Hi guys are all mk1 wheels the same in their spline size?
If not when did the change take place?
Is the early mk2 wheel with the 4horn buttons the same as mk1?

Think early Mk2's have the same spline size as Mk1's, and then they increased in 87 or 88

There appears to be spline adapters available to change from the small MK1 to the later type big spline. Thinking of changing your wheel?