grant,
i have recently had a VS diff installed into my FC. They did as you said and used two short axles. But be careful as i think this combination may be shorter than you want as i have had mini tubbs fitted to accommodate 18x8 inch rims.Do your home work and measure the commodore diff that you are intending to use. Also depending on the commodore there are different size axles so you might want to speak to a diff expert. There is a photo spread of this conversion in this section around december/january.
regards brett
Thanks for the heads up Brett, I will check it out as you said.
cheers
grant