Speedometer

I just bought a new speedometer cable from O'Reilly. I think it was $8. Actually, now that I think about it, it was $7 at Auto Zone and O'Reilly matched it. Let me see if I can find a part no...

Pioneer CA 3002 The application is for a '72 Dodge D-100, 318, auto, lower cable. It is 63" long and a perfect fit with the correct ends for use with a mechanical drive speedo.

Well, I just reread your post. I think what you will run into with an aftermarket speedometer is that they take an end that screws on. Your cable probably pushes on. You can buy an adapter or get a new cable...
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