It depends on the size of the rear cog and the length of the frame's chain stays. 56-58 is common for 26 inch wheel ballooners and some of the 28 inch single tube pre-ballooners. When in doubt, buy the longest length of chain you can get and use a chainbreaker to shorten it up.
24 skip-tooth (really 48 tooth by today's standards), is a good front chain ring size. I think those big "sweet heart" sprockets that ran 26/52 were too high-geared. 24 front and 10 back will give you a nice, semi-low ratio for a single speed. If you're using a 3-speed, you can even drop as low as 24-12 and have a nice climbing bike. But in order to use those friendly ratios, you'll want the longest chain you can get, probably a 58, then trim to suit your chain stay lengths.
