early v8 speedo drive question

I am using a 46 ford rear with 3.78's and shortened closed driveshaft in a hot rod.
My question is about the speedo drive. Does this have to be matched to the rear ratio? I have a drive assembly from another torque tube but no gear for the internal shaft.
Any suggestions for suppliers of these gears?
Thanks

 

1930 (round speedo)--1948 drives interchange. A couple of ratios are available in repro from the Model A dealers, driven gear and "turtle" housing only. I believe all drive gears around the shaft are the same from probably '28-48, but would want to check that. At least 5 or 6 driven gears are out there...
There's a chart in the back of the various '28-48 parts compilations matching gears to rear drive gear/tire combo. If you're tires aren't on the chart, you'll need some research to try to match their diameter to a tire shown. The basic 3.78/regular passenger tire gear is common, some other ratios are hard to find.

 

Thanks for the quick response. I'll check the model a parts route and see what I find.