Not a "bolt in". I know the driveshaft is different. 63 had a flange on the rear of the trans, where the later all synco 3 spd has a slip spline. the speedo hookup is also different, but is solved by using a 66 "A" body cable. I am not sure about the bell housing. I have both types of trans/bell housing, and will try to measure. Also not sure if the 63 shift linkage will connect to the later trans without mods.
The super six with a good carb is a wothwhile improvement, along with a larger exhaust system off the stock manifold.
PS: there is no difference in performance in the 1 bbl or 2bbl exhaust manifolds. only difference is the choke pocket, for the auto choke, and the 1 bbl manifold pocket can be easily modfied.