If you want to rebuild your wheels, the best current choice would be 650B which are pretty close at 584 mm BCD to your current wheels. Actually, your front wheel is probably not worth rebuilding, but the 3 speed rear hub is probably worth salvaging if it is working well. The smaller diameter 650B rim would require that you move the brake pads downward by 3 mm so you would have to check to see if your brakes have that much adjustment. 650B tires are much more readily available than 26 x 1 3/8