65 Speedometer Cable and Gears

[orlowted]

OK - Now that I have the instrument cluster all over the garage and the Fuel Gauge works like a charm...It's time to get the speedometer working. The symptoms are erratic bouncing and sometimes not working at all. I have a 289 with a 4 speed toploader. I figured I could just go into the catalog and order a cable and all would be well....Not a chance. They want to know all kinds of good stuff like axle ratio, # of teeth in gear, etc. It prompted me to thinking....The car was a original 6 cylinder with a 3 speed. I believe it is the original cable so I guess it is not going to work with the new engine,trans and axle set up I have. My thought is to just replace the gears that go into the trans and all would be OK. Any thoughts on this???
What is the easiest way to determine axle ration? I think once I have that - I can order the gears and give it a whirl. I believe the cable to be OK so I think I will start there. Any help is appreciated.

TJ