Need Speedo gear for my 64 dart

Well I have news, so far I am unable to find the gear I need, I am also unable to findout if the gear I need ever existed.

Talking to the parts guy at the local dealership, I have delt with them for 30 some odd years, they are telling me that the 21 tooth gear is the largest that was available.

the gear reduction things will not work because they are for later years also.

I will keep looking, but so far my best bet is to reprint my speedometer face. which doesnt do much for the odo :)
there must be a solutoin other than replacing my trans.