I think you should get rid of the Powerflite and fit a manual with overdrive... that will give you greater longevity and driving comfort whether you take the other steps or not.
Line (or align) boring will depend on how straight the block measures up in the crank tunnel. If it's straight, no need to bore.
Balance would probably be a good safeguard and could give you a minor improvement in smoothness.
If people who know these engines (George Asche etc) recommend the bearing mod, I'd go with it.
I'd also look at enhancing the front brakes, either going to larger drums or to discs, but try to stay away from power boosters unless it already has one.
