there are three different style speedo drives in the muscle car era. The early one, like my 65 Cuda has includes the pinion adapter as part of the speedometer cable, the next newer style uses a larger diameter adapter and a screw on cable, the last style also uses a different large style adapter with the bayonet style cable attachment. The last two can swap AS AN ASSEMBLY pinion, adapter and cable.

1st style

https://images-na.ssl-images-amazon.com/images/I/511j7NTuiiL.__AC_SY300_QL70_ML2_.jpg

2nd style

https://www.forabodiesonly.com/mopar/attachments/dscn5285-jpg-jpg.1715349945/

third style

https://www.forabodiesonly.com/mopar/attachments/100_5548-jpeg.1715470767/