With the 4 belt engine it's failry straight forward, remove one belt.
I'm guessing you have a later serpentine belt engine. The idler is different and unlike any other LR engine of the time, it runs on the grovved side of the belt and has a plastic pulley, larger in diameter then the one currently fitted. The belt is also shorter.
I'd suggested the easiest would be to find a secong hand pump and swap it over.