You might want to consider a toolbox fuel tank combo, or other fuel tank that fits into the back of a longbed truck. Then get a way to hook up a fitting from the bottom of the tank to the generator fuel cap. If they are about equal height, you might get gravity fill- without overfilling.
As for personal what I have done, it is a boat type fuel tank with a fuel line and hand prime bulb on it. It can hold about 6 gallons and if slightly above the generator fuel cap, it will slowly drain into the generator.
After a few hours, you can take the boat fuel tank and refill it, while the generator keeps running on it's built in fuel tank. Then prime the bulb again, and the small tank will start feeding the stock tank again.
I am hoping that you have a dually truck, able to handle the extra 500 pounds you propose!
Good luck!
Fred.
