Ron, so .... you're going to try and drop your RV's Ford chassis 55 gallon tank?
How you going to empty it first .... and what are you going to empty it into? After you empty it into something, are you going to throw all the gas away, or somehow pump the gas from it's temporary container back into the tank? Of course all this has to be done ultra-safely.
The above questions/issues are why I'll raid the piggy tank and have a repair shop do it if/when ever needed. Those issues are also why I recommend putting the best new fuel pump money can buy back in so you never have to do it again.
I participated in a another forum discussion about in-tank RV fuel pumps - in which I tried to make the point that truck chassis manufacturers should install dual fuel pumps inside the tanks so that the chance of one failing and letting you down a long ways from home would be zero. Sadly, I didn't get very far with my logic in that discussion.