does a 1966 ford galaxie and 1968 thunderbird have similar
That's right, the tie rod ends from the 70's intermediates will not work with the early galaxie tie rod (different diameter threaded section). I can confirm from experience that they will not.
The cars you should look for are 77-79 Tbirds. You can also use parts from Montegos, Rancheros, Elite, LTDII, Torino, Cougar, etc but I don't know the exact year spread of those models.
You'll change the spindle and everything outboard of it. Your factory spindle will not work with the later model disc setup. You also will want to change to a dual reservoir master cylinder.