It definitely depends on several factors, but I think the main one would be brake reach. Most bikes made for 26 x 1 3/8 wheels will take 700c but may require smaller reach brakes and you may have to lose the fenders (mudguards). 650c might require only a minor adjustment. I'm not sure you'll be able to get any brakes to reach to a 26 x 1.75 rim; if you find anything that fits it'll certainly have a long reach and will be relatively weak. Still... worth a try.