Hope my memory is correct on this. I have the same speedo/transmission. I used a standard Ford speedo gear adaptor at the transmission but I installed a reverser at the speedometer so the speedometer spins in reverse correctly. It could be mounted at the transmission end if there is more room down there.
https://www.google.com/search?q=spee...=1498217028593
You have to check to make sure the adaptor as received is set up to reverse the cable twist. They can be set up both ways - the other way just provides a right angle adaptor. They can be changed by disassembly.