[AZKen]

Generally speaking there are two reasons for rubber hose. One is to enable removal of tank, like the filler rubber hose. The other is for vibration/movement, as you know. Generally if the tank and the fuel line are mounted to the same thing, like the cab or the frame, there is no need for rubber because in the frame mount example, the tank and the frame and the line move together. Rubber is needed when the line travels along some other part or it leaves the frame. Like when the line heads to the motor/fuel pump. The frame and motor are going to move independently of each other. Therefore a flexible line is needed there. I.E. rubber hose section.

In a 6066 truck, the tank is behind the seat. Mounted to the cab. The cab is mounted to the frame. The cab and frame "move" independently, So the hard line is attached to the sender and travels down thru a hole in the cab and towards the frame. The transition at that point needs a rubber hose from cab hard line to frame mounted hard line. Then the hard lines goes all the way to front and has the aforementioned rubber hose to pump.

Same general story, as you will notice, with brake lines.

If you are unsure or the factory used a hose, no problem adding, except it's another two leak points and Chinese rubber hoses deteriorate.

Maybe Funky can tell us or show a pic of any rubber on the hard line for a Burb, should be the same for a Panel. Also: what is the vendor and part number of that tank?