1st, make sure your new distributor has a gear that is compatible with the stock roller cam's gear. Flat tappet cams use a different gear material, and mixing the two makes a mess of chewed up teeth. I do not know of a stock points type distributor for a roller camshaft, so you may be switching gears or need to go with an aftermarket distributor.
As far as the transmission, do you need an AOD, especially when the c4 can be built stronger for less? No. But will you wish you had installed overdrive? Probably! I sure wish I had on another classic I own. I can not tell you about driveshaft length, mounts, yoke or u joint issues, just that overdrives are a good thing if you ever get on the road.