Yup, somebody converted it to a live rear axle (both wheels driven), and used clamps instead of bearings - crazy and dumb, but...
I'd get that axle off of there, as well as the clamp parts. Then try to gring or cut the welds holding the wheels on - if you're lucky you can get one off, then you could remove the sprocket and its hub from the axle, slide a pillow-block bearing onto the shaft, reinstall the sprocket, and slide another pillow-block bearing on there, and reattatch the wheel. Get pillow-block bearings that have set screws, and that'll lock the shaft in place side to side.
Surplus Center is a good source for bearings and lots of other bits.
Dura-Roll,Brands, STAINLESS STEEL ROLLER CHAIN Brand new, stainless steel roller chain. 304 stainless for use in applications with harsh chemicals or
www.surpluscenter.com
If you can't get one of the wheels off, then yup you'll need a new live axle kit. Or go back to one-wheel-drive.