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If you have an early a (up through 65) and install a 66 or later transmission you'll need the 66/67 "problem solver" cable. This style of cable has the small nut used on the early speedometer with the large nut on the transmission end to fit the speedometer pinion adapter. I've found 3 more while cleaning out cabinets of my 65 Dart stuff. All of them have the firewall grommet. The bottom on in the picture will need the inner cable, available as a kit at your NAPA, maybe Autozone, etc. One of them still has the pinion adapter on it (this one I was using in my 65 Dart with a later transmission). $25 shipped to anywhere in the US.