How Do I hook up speedometer?

I have a 66 CJ5 with a buick 350, SM465, Dana 300 and 4.88 gears. How would I go about hooking up a speedometer? Is this even possible? The stock cj5 speedo is still installed and I would love to use that. Does not need to be exact, just want to have an idea of what speed I am doin. Thanks Zach

 

I will try to answer this.
There is an early type of D300 that uses the same type of gear/adapter that a D18-D20 transfer case would have. The replacement gears are almost impossible to find. They are all metal gears. The speedo cable would attach to the pass side of the transfer case. Your stock 66 speedo cable would hook up to this type.
All later D300s have a small aluminum adapter/retainer on the drivers side, that spins and adjusts for different size gears. A bolt and forked tab hold it to the case. It is sealed with an o-ring. The gears for these units are readily available. There are many different tooth counts so it would be possible to really "dial it in" for your particular application. If I am not mistaken, your stock speedo cable would hook up to this type also.
I don't believe it's going to be that difficult if you have a cable. Just crawl underneath and see which style adapter you have and its location.
Even if your stock 66 cable end won't work on the D300, I think a later 80s speedo cable would as the speedo head threads are possibly the same size.
hope this helps

 

Mine Dana 300 Is a 80' so that is as early as they get. The speedo cable is gone from my speedometer, so I will need to buy that to. Thanks A lot.