I have a 78 D100 and the steering wheel was cracked in a couple places so I bought another one off of eBay. It doesn’t want to go on. The shaft has a blind spot in the splines but the new wheel doesn’t. Shouldn’t matter because the blind spot is recessed in the shaft. Were there different splines? Different number of teeth in the spline? I’m starting to think the new wheel has more teeth.
old wheel part number 4019001-71589-1
new wheel part number 4019001-71589-2

 

The "blind spot" is a centering position on some of them. IF the spline count and diameter are the same you could remove one/two of the splines to make it fit.

 

I counted the splines three or four times. I think the old wheel/shaft has 36 and the new wheel has 39. Does this sound right? It looks like I paid good money for a wheel I can’t use. ☹️