If you're any good at metal work and paint, I have a slightly beat up 1981 CB750 gas tank. I got it off of EBay when I bid on a petcock, and the guy didn't tell me that it came with a gas tank. I guess that explains the $20 in shipping costs for a petcock. :-)
Anyhow, if you're interested, drop me a private message, and we can discuss it. If not, no hurt feelings.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.