The black tops are different, but not sure how it affects installation into the RS.
the current model Zetec, as used in the Focus and Mondeo is a very different engine to the earlier Zetecs, both visually with it's black plastic cam cover, and internally. Starting at the top, the Series 3 features new injectors - end fed unlike the side fed units on the S1 and S2, and with a twin jet spray pattern. Solid tappets with adjustment shims replaced the hydraulic predecessors and the cam belt timing tensioning setup has been revised. The pistons are teflon coated to reduce friction, and the bearing caps are on a single piece frame to increase strength. The water pump was of a new outboard design, with large vanes for improved flow. The block was strengthened - a larger amount of metal between the bores is clearly visible in comparison with the S1 and S2. The oil filter mounting became integral to the base of the block and the sump gained a windage tray and baffles to reduce oil surge. The sump's webbing was also improved in an effort to combat block flex.