Zetec Thermostat Housing - Depth?

[Tatey]

Does anyone happen to know the depth of the Zetec thermostat housing? I currently have 50mm clearance between the back of the head and the chassis cross member, I am dubious as to whether or not the housing will fit and I don't really want to take a punt to find out it wont.

[baz-r]

my silvertop needed the tr tube at the back of the head stepping back 25-28mm above the bellhousing

head rear face - to rear edge of housing unit = 80mm