Hi Scott,
Im looking at doing almost the same conversion. My mk6 fiesta is the 1300 finesse. I have acquired a mechanically sound 1800 zetec mk1 focus with the view of transplanting it into the fiesta. Im no wiser than you seem to be, having been asking the same questions. Unless someone fills us in, ill keep you posted on what i discover about the conversion, if that helps. Good luck.