69 speedo cable routing
 

On my 69 the speedo cable comes out of the passenger rear of the Muncie tailshaft. Then it could go over the top of the trans OR under the trans headed to the firewall. Which is correct?

From the speedo, it runs to the right and thru the firewall, across the back of the engine over the bellhousing, drops down along the right side of the tunnel and back to the trans. I routed mine over the heatshield to help keep it close to the body under the passenger side floor.

I can confirm this as I just replaced my speedo cable yesterday and routed exactly as described. I believe you'll also see a couple of hooks/clips along the way where the cable can clip into.