1965 plymouth valiant transmission gear linkage

Good morning Charrlie_S, it's been awhile to ask you a question :) Can you tell me is the standard three speed on a 66 Valiant is the same as a 65 sir ?

No the 65 has a flange on the output shaft, where the driveshaft connects. A 66 has a slip spline. The 65 trans does not have a syncro on 1st gear. Later trans does (not sure what year that started).