It is about 30mm. I can confirm tomorow when i look at my rail.
I was going to use one from a 96 Ford Laser i think it was... bolts to the side of the head... but any will do then you can run the thermostat in it... just tap into the zetec head....

Are there any notable water jackets or oil gallerys to be avoided around the area when drilling and tapping?

not sure. i have seen it done successfully. just have to inpsect before drilling.

Now thats a thought, I have looked into slim thermostathousings before but never occured to drill some new holes! Genious! I went looking for a bolt on job, twas a bit more difficult and time consuming than the choose your own adventure suggested by Mickas.
You could try hendo for an Edis, there was one in the mondeo I sold recently, He may not need it. I have a spare coil pack too, now I got my other motor.

Found this in my pile of Zetec pics.
Not sure what thermostat housing it is.
Appears to have a pipe to the heater also.
And temp. sender at the back also.

Good photo. Being a bit reluctant to start drilling the head i was thinking maybe a 2-3mm plate drilled as per standard plastic housing then studs welded on to suit new thermostat housing; recover what you lose in the plate by 'buffing' the new housing back a little.

Tex - Saw your ST170 thread and wondered if you might have a spare coil.....are you a beer drinker?? Thanks for the lead on the EDIS i'll PM Hendo and see if he likes beer too.

The housing is very similar shape to the one off a VB-VH commodore, but the holes are completely different.

The sump and mounts turned up from Retroford. The quality looks excellent. Hope they fit as well as they look.

Is there anyone out there that knows current ford part no's for:

Flywheel Bolts 1.8 blacktop zetec 2002
Clutch cover bolts for same
Pinto spigot bearing

I'm told the local parts dept can't do much without a VIN no so any help would be much appreciated.

A local ford spares dealer should know. Spigot brg is the same throughout 4cyl fords from the '60s , mine cost'd $34 trade!!
Flywheel bolts should be same as 2.0 zetec from 1992, Clutch cover bolts are M8 high tensile bolts, similar to pinto.