I always feel it is better to rebuild, refurbish, restore, refinish what you have you already knew you engine's problems. Unless you want to go bigger but that's a whole other project that can be dealt with later if you chose. Since you got a deal on a runner to stick in its the obvious choice. With regards to your Questions you really don't need a balance job, it was good for factory right. Boring is conditional shops all want to bore everything because then they sell you pistons, marked up double and make more money, if the pistons came out without having to cut ridge or no ridge at all you have a good candidate for hone only, lastly hardened valve seats are more required to run big h.p. springs if you are staying close to or stock there is really no need, yes they will wear but everything wears, hell I'm more worn than I was 20 years ago, so if you are planning on hot rodding yes, if yours are really worn from super high mileage yes, if your planning on running 15,000-20,000 miles a year yes