KZ650 aluminum swingarm?

Hello, I'm interested in replacing the stock steel swingarm on my KZ650 with an aluminum one, but I have no idea which one would fit. I looked around in the forum and didn't really find good information on this. Which aluminum swingarm from another bike would fit up to the KZ650 frame without much hassle? I'd prefer the same length as the original one, with the twin shocks. I was thinking an old dirt bike from the 70's might have something, but don't know for sure.. Maybe Kawasaki used a common style for most of their bikes back then? There's so much about this that I don't know. Thanks. 

Fitting an aluminum swingarm from another model can be done.
The 650 can usually take whatever the 900/1000 might squeeze in.
Most commin were GS1100, Zephyer 550/750. ZRX1100/1200.
All custom fitting involved.

Some aftermarket manufacturers made some as well; CalFab, Metamatch (SP?), JMC etc.