'65 Dart /6 A833 swap - clutch fork, input shaft, speedo gear, crossmember questions

Measure the diameter of the input shaft. I recall 65 uses a smaller pilot bushing.
Nope, not on a manual trans setup. The automatic converter hole was smaller in '67 and earlier slant's and 273's, but, not a manual pilot bushing for a manual trans crank. If you have an automatic crank that hasn't been machined for a bushing, there are conversion bearings out there that can be used. They fit in the converter hole instead of the pilot bushing hole.