A couple more things. Sun makes a CR18 rim in polished finish in the 26 1 3/8" (EA3/ ISO 590) size. No one else does anymore. You will almost certainly have to build the wheels up custom yourself, or have them built. (please do not put black rims on that bike!) 26 x 1 3/8 was once a very common size, but has been fading out since hybrids essentially replaced 3 speeds in the 80s.
700c are never going to fit. Forget about it. If you want to be blasphemous, you could go with French 650b (ISO 584 /"27.5") size, as this size has seen a renaissance and is now widely available. It would give you more choices in rims and tires. 650B is only 3mm smaller in radius and they'd almost certainly swap in. Your bike may mutter insults at you for doing this though.
What on there now? Looks like Schwinn S6 597?