40 Speedo to open driveline

[Pech33]

I am contemplating a chassis switch due to rust issues in critical places on the frame on my 40 convertible. In looking at the issues, the speedometer gear is in the enclosed driveline. Is there an adapter for the speedo if I want to keep the original 40 three speed mated to an open driveline to a Ford 9" differential. If not, how do you get the speedo to work?

Any thoughts?