[kipps]

Buy new sending units as well, if you can afford them.

Block the truck up high enough so you can comfortably lay under the tank, and lower it to the ground with a knee and a forearm.

Remove the hardest to access bolts first, leaving one easy bolt on the front and rear tank bracket.

Cut the hoses going to the tank, so removal is just a matter of dropping the tank right out.

Swap the senders left to right, so the sender outlets face outward over the frame rails. This lets you make a longer loop of fuel hose, and considerably eases future tank removal.

Find some way of capping the tank fill and vent opening on that full tank before you attempt to lower it. Otherwise, you're going to be splashing ancient gasoline onto your face when lowering the tank. Several disposable rubber gloves snapped over the opening and hose-clamped in place will likely do the trick.