What you need:
Speedometer cable, '66-'67 A body; 63" long, has 5/8 and 3/8 screw-on fittings on either end. The 3/8 one fits your speedometer, the 5/8 goes to the transmission speedometer drive adapter.
More Information for PIONEER CA3002
View attachment 1716347012
Speedometer adapter; '66 and up, all transmissions use the same adapter.
Post a wanted ad or contact Brewer's.
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Speedometer drive gear; '66 and up, all transmissions, tooth count dependent upon your rear end gearing and tire size. Again, post a wanted ad or contact Brewer's.
View attachment 1716347024
The adapter you have is a later model single piece with the cable- yours just became separated from the cable and is not useable for your application.