Those two straps can be a PITA to remove. I usually just unbolt the dashboard side and then bend them up against the back of the cab.
Make sure you disconnect the sending wire, close the petcock valve, disconnect the fuel line, as well as remove the leather/rubber grommet around the fill tube before trying to lift the tank out.
From the drivers side, just lift the tank and twist the tank to your left as you pull the tank twards you and she'll slide right out.
