[nutz4sand]

As far as I know the Mustangs are solid axle. A lot of the later T-birds were IRS and the diff aint to heavy. I got one here thats supposed to be out of one but I have never seen one in a scrap yard to know. Its an IRS diff from Ford and its aluminum.

I do not know the use you plan to use it for Wyatt but your comment about the wheel and tires compo (compo? ;] ) and pulling logs out of the woods would make me run nothing BUT a car diff. If its gonna be a workhorse a few extra pounds are a good thing if it holds it together.

If its a racer then its a different story.

Heavy duty and lightweight usually mean $$$$.

If you were building just a one seater and wanted 4wd for say the mud then car diffs might not be needed. But the tires size may destroy anything quad sized.

Soooo what size tires are you planning on it having?

As for a chain drive front "diff" an older Polaris 4x4 quad used to use a chain drive front setup. Ok for what it was made for but not too much more.