the zetec pistons as you say stu are bigger at circa 81mm where as the cvh is circa 79.96 or something like.

if you keep the 1.8 head then the CR will go to about 10.5 CR I reckon... - just estimating based on the dish in the 1800 pistons (zetec are flat)

not sure if the zetec pistons fit straight onto the 1800 rods - but I assume they do. if anyone has a zetec rod or piston handy to measure the width of the con rod then I could tell you.

the gudgeon pin should be the same diameter as most fords are.

ooooh and stu 241lb/ft??!!! get your sig updated then without the "does it really need a turbo with that low boost" setting