Technical 56 Ford F100 worm gear

The new replacement worm for my 56 Ford truck has a different inner spline than the original.
The new gear has wider and fewer splines.
I researched and this new style is all that is available (at least that I can research).
Not really wanting to buy the gear/shaft combo) unless I have to.
Have any of you Ford guys encountered this issue?

 

Where did you find that? Did you try C & G Ford?