I have seen the whole episode. From what I remember, the axle isn't special, the mounts are to get it that low.

The eipsode also says how much they bought it for, and sold it. It wasn't crazy prices for the truck, so sensible enough to do the mod.

Would I have done it, no. Did they ruin a perfectly good truck,highly debatable based on preferences. Each to their own, I liked what they did.