I dropped the 80 gal tank on my 79 MH.
I drove it to near empty before pulling the drain plug. It still had 12 gal in the tank. I drained it into a modified 5 gal bucket (with an access slot cut on the side to be able to reach in and replace the plug).
Be aware that just by dropping the tank straight down, you may still not be able to reach the sending unit. You may have to slide the tank out from under the vehicle. Careful measurements and ramps for the rear tires may be needed.
Gasoline weighs 6.17 pounds.
With 10 gal left in the tank, you are looking at 100 pounds plus.
The bolts for the straps were hard to reach and for some reason, I did not have the proper socket in my assortment. I ended up getting a 19mm socket from sears that is 1 5/8" long, which allowed it to fit over the threat to reach the nut.
If you drop the tank replacing the rubber fuel lines should be included.
Most of the wires are running on top of the drivers side chassis frame.
1983 310 Classic Motorhome
1997 30' Excella Trailer