There were 2 similar but different speedometer gear assemblies. One stood higher out of the transmission than the other and the gear had a lower helix to it.
I appreciate your looking for me but this is the wrong type. It should have a higher helix to he gear and measure approximately 4.16 inches in over all length
I too just acquired a 1920 Dodge Brothers touring convertible. It’s in excellent shape except to say it’s sat for several years in a heated garage and the gas is all varnished. So I have to go through it all before attempting to start it.