Hi Jarobi, welcome to PF

first of all, the head probably belongs with the block, as the heads on the 1.8 and the 2.0 are the same. The common thing is to take a standard 2.0 engine and just fit a sump and pick-up pipe from a 1600/1800 fiesta or escort/fiesta model.

The throttle body size is correct for either a 2.0, or a 130bhp 1.8 model. unfortunately i'm not any good with part numbers, so i can't tell you where your manifolds or ecu are from, but i'm sure someone else on here will know better than i do

as for a missing idler, no idea why! i'd probably put it back on there just to be safe! no reason it should affect timing, becuase timing is set by a bar on the back of the cams and it has completely adjustable pulleys (no keyway).

hope this info has been of some help