Body carts. Have you built one?

I am getting stared on my 71 Duster restore and am looking at body carts. Has any of you built your own? I like this one http://store.uscartool.com/mopar-car-moving-wheel-set.html but cannot justify the $400 when i maybe able to build for less than half. Anyone have any plans/dimensions for building your own?

Thanks a lot.