if you go for n/a just get a 1.8 zetec with loom and pre pats ecu.
mod the engine mount but cutting off one of the lugs and welding another one on + drill the hole.
wiring is easy www.s2rs.co.uk have the diagrams on the site forum and a fair few people have done the change on there. i just took my 1.8 zetec out of my mk4 and put in a rs2k i4 lump so trust me na zetec is easy peezy and it will be BETTER on fuel than ur 1.6 xr3i is with more power so its a win win situation i think.
best way to do the mount is get a spare and do all the welding on that using the zetec for reference of which lug and the extra hole you need to weld on/drill out then when you do the swap its one in one out. pics of the mount are here:
http://www.escortupgrades.co.uk/Escortupgrades.html
i didnt weld the extra tube support and was using 130 spec lump and had no problems at all with it, had it in for a year then took out tuesday was a good conversion nice and simple yet a fairly good end result