The silver top engine (early engine) block was not used in WRC so all you can use is the std oem waterpump that fits in your block. they used the std pump anyway.

The blacktop WRC block as pictured was modified with a pear shaped hole in the side to assist flow

They have a round hole as standard

The WRC engine used a regular ford water pump that was welded and machined to match the pear shaped hole. It had an o-ring groove machined round the mating hole of the pump to seal it. Other than that it was pretty much a standard Ford Item.

How do I know? Because I bought of the last ones from cosworth and used one on my own engine.

Cosworth originally developed the Focus WRC engine but lost the contract to mountune.

If you are using the black top WRC engine I would use the later OEM Focus RS water pump

This was not available during the WRC days but was brought out for the Focus RS road car a bit later on.

It uses a much larger housing and impeller to cope with the added heat of turbo use.

I bought a new Focus RS pump from Ford and had it welded and machined to an oval to match the block

I also had it o-ringed at the same time to make it seal nice.

Either way a standard waterpump from your local ford dealer should be your starting point.