I used a 1/5 scale chassis and emaxx front/tranny/rear clips. Put on dual 7XL on 4S. Topped it off with a FG rally body.
Email
Bill@rcalloy.com for custom shafts. He made 7 inch shafts for my application.
I think converting a truggy is a perfect idea. I even bought a Pajero 1/5 scale Dakar body for just such a conversion. The Pajero would have a smaller wheel base, so you would not have to use two custom shats, you can keep the stock rear shaft and just get a custome front one.
Good luck.