UPDATE from the OP.
Scott, I appreciate the story of your Russian barn find. It must be a blast to ride.
I have discovered that the compression in one of the cylinders on my bike was around 25 psi so I have removed both heads, cylinders and pistons and had a local airhead expert, Dave Clark who owns Forever Endeavors in Pacific, MO, install new rings, valves, guides, etc. and ensure all are within factory specs. In addition, I had Dave re-spoke, true and balance and install new tires on both wheels that are now back on the bike.
We have the engine re-assembled and one of the carburetors rebuilt. Unfortunately, the other Bing had one stubborn screw out of the four holding the cap on and the main body was cracked while sttempting to remove it. We have JB welded the piece (see photo) and hope it will hold. As you can see, the screw still fits the original threads.
After completing the left carb rebuild and installation, the new OEM-style exhaust needs to be installed and the tank will require repainting, restriping and re-installation. Lots of fine tuning and smaller parts installation will be required before the bike will be ready for a test ride. I hope that can be accomplished this Spring.
BTW, is it possible to TIG weld this broken piece after JB Weld has been used?