Mike-
I am by no means an expert, but here is my opinion. The 235/261 will basically be a direct bolt in replacement for the 216. They use the same motor mounts and the same bell housing pattern. The 230 will not be so easy. The 230 uses the more modern V-8 style side motor mounts and bell housing pattern. So, basically, to install a 230 would take the same amount of customization and effort as to insall a 350. If it were me, I would definately hold out for a 235.
As far as the trans goes, I don't think you can get a full synchro'd unit to fit with the torque tube. The three speeds that were used until '54 (the last year for the torque tube) were only synched in 2nd and 3rd. I don't see any reason you couldn't use one of these, but keeping the stock floor shift may be a sticking point. As I recall, the non-synched shifter dropped directly into the top of the trans, where the later trans used linkages that exited the side. I'm sure you can add a floor shift to the later trans, but I'm not sure about keeping the stock appearance.
I am certain that somebody else will reply that has more knowledge than I. Good luck!!
