There are generic "stars and bars" decal sheets available. I guess it depends on how detailed the markings on the model are, or how detailed you want them to be. I always got mine from Squadron, they have, or had, sheets with many different sizes.
As for the props, figure out the size of the ones you need and get the closest matching kit.
Really old kits, like the one you describe, could be just about any scale.
Here is a nifty program I have used for years (I am a masochist, I do a lot of scratch building) to determine scale:
scalemaster
Easy to use once you play with it for a while.
Oh, and Squadrons website:
Squadron