I think you can do it with diesel, but petrol has to be a sealed tank or boxed in gas tight.
I would use steel rather than wood, if it leaks the wood saturates with diesel......a fire (i.e. wayward ciggy or welding sparks etc.) and you've got a slow burning, but difficult to extinguish car fire!!
You'll probably need the filler on the outside of the truck to avoid spillage and fumes....derv stinks!!
Like I said, I'm not 100% sure on this....google it??