if its going into a mk5 or mk6 escort then yes it will go onto the original box but i believe that you will need to use the 1.6 flywheel and clutch ( i could be wrong though)
if you want to use a rs2k box you will need a rs2k flywheel and clutch as the splines are larger on the rs2k item, also the flywheel may not have a trigger pick for the crank sensor, i know they have holes in em but not 100% sure if it will work a zetec as the rs engine has the crank sensor pick up from a ring inside the sump on the crank as apposed to outside on the flywheel.