1.  Would image a new door seal (and window seal?) along with some Dynamat-type material under the cab upholstery, panel between the engine, and under the floor would make a big difference.
2.  New LED light fixtures.  LED bulbs in a 40+ year old incandescent housing aren't worth the $20 painful lesson.
3.  ?
4.  We've had air foils in several Axial Flows over the years after having breaking the originals - they are good and bad. Would I take out a factory sieve in operating condition to replace it with an aftermarket?  No.
5.  Salvage yard?