You might be able to modify your NV4500, replace the tail shaft and housing for one with connection for mechanical speedo. I think there were a few early years with that set up. I will be using my '47 speedo with an '88 5LM60 (early NV3500). There are off the shelf convertor boxes that take the digital signal to run a motor that connects to the speedo cable. I decided to build my own. Not a simple solution, but not impossible. Here is a link to a video I made of the test run, I hooked it up in a '90 truck along side the stock speedo.
