Nice truck !
They can work well for wfp sole trader with a bit of thought, very well in fact.
I ran a Ford Ranger supercab last 5 years. Only sold this February and went back to a small van. Miss it !
Re tank : I had one made for me by Stephen Scargill.
A 500 L baffled lay flat that fitted tightly between wheel arches in load bed.
If its of interest I was going to put it up for sale some time as not needed. I am on south coast though ( 7 miles from Brighton ).