26" means many different sizes; so here the ISO size that have been called 26":
597, 590, 584, 571 and 559 - these are the bead set diameters in millimeters
http://sheldonbrown.com/26/index.html
You might like something like my SR Sierra Sport; which I believe was originally equipped with 590, and now has 571 with 28-571 tires. Mine is the same as uciflylow suggested. It is a very early "Mountain Bike" with no suspension and with a chrome moly frame and forks. I have a 130mm OLD hub in the frame, but a 126mm would work well; a 135mm would not work at all. It is around 2/3's the weight of my World Tourist.
I would build it up from scratch. My SR frame came from eBay, my GT came frame CL.