I think the previous owner may have had fuel problems, because those canister filters under the truck are not the stock setup. The OEM setup only had a filter under the hood at at the carburetor inlet. There may have be a reason (bad gas?) the PO added more filters.
If you want to drop the tank, its fairly easy to put a flat board under the tank (2x6 or 2x8) and then support it with a small hydraulic jack. Then unbolt the tank brackets from the frame and lower it down slowly until you can reach the fuel lines to disconnect them. Do not try to remove the bracket & straps from around the fuel tank unless you want to buy all new straps.