I had heard of that bike but never seen any pictures of it. I am sure you have tried the 305 message board but if you havent check it out and find LOUDMOUSE(Ed I believe his name is),he seems to be the "go to guy" for obscure CB/CL 72-77's info. Also you may wanna try Team Hansen,Bob Hansen(RIP) was the head service guy for Honda America in the '60's IIRC he passed away a few years back but the company is still going and they may be able to point you in a direction.
Please keep us updated on what ya find I myself ride and road race CB77's and would like to know what you find.
"The world does not need another restored bike."