Shift Linkage Interchange from a 65 Slant Six/904 to a 66 273/904

The '65 has cable linkage, the '66 has mechanical linkage. Two completely different transmissions and linkages, not much of anything interchanges that will be of use to you.
Best bet for you would be to get a '66 steering column and shift linkage and swap that in, or an aftermarket floor shifter.
You will also need a different driveshaft ('66 Valiant/Barracuda, Dart is different wheelbase/driveshaft length) since the '65 uses a ball and trunion and the '66 uses a slip yoke.
You'll also need a '66-'67 speedometer cable to mate the '66 transmission to your '65 speedometer.