As long as the mounting points line up, especially at the back, they should fit across 1979-1983. The shortness is probably after where they bolt on near the rear pegs.
If you put them on EBay, be prepared for a LARGE shipping bill. It's not cheap to box and ship them so they arrive in the best shape. Trust me...I had a factory 4 into 4 set from my old bike, where I was selling the set for $150, and the shipping came to about another $150 in the US.
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.