Other than the gas tank and transfer case the underside of Toyota's are pretty high and tight. I'm not sure I've seen anyone really armor the gas tank (some will relocate it on a more buggy or flatbed style build) but you need a solid cross member under the transfer case. If you're running dual I love the cross member that I run. I got mine back when it was a Marlin Crawler product, but it's the only TG product that I would buy if I needed another cross member. It's beefy. I don't see anything currently offered from Marlin Crawler, but Budbuilt is another solid product.
Jeeps have a much flatter belly which is why you'll see a lot more plate protecting them.