1941 pickup 4-speed speedometer gears

[504d]

I decided it was time to get the speedometer working, which hasn't worked since I bought it.
The inner cable was broken where it attaches to the trans.
That's on order.
Today I tried to figure out if the gears were ok, but I'm not sure.
My thought was that I shouldn't be able to turn an inserted cable if the gears were ok, but I could.
So I removed the speedometer gear case, and when I turned the cable, its gear turned.
The gear looks a little worn, and the worm gear on the shaft a little worse.
But I'm just comparing to pictures.
Does it seem logical that one or both of those gears should be replaced, or is my test bad?
Then, what gears are correct?
The drive gear has 21 teeth and the case says 21.
Is there a more than one 21-tooth gear?
And which worm gear is correct?
When I search for the worm gear for 1941 pickup,
they assume open drive shaft, but mine is closed.
I'm having trouble narrowing the choices to something specific.

Thanks, Steve