where are they ?

Under exhaust port no 4 stamped on edge of bell housing mounting flange

ta ;-)

any way of finding out how old it is ?

I guess you will need to contact ford.

They were made from 2001 early ones had a silver top newer ones have black tops.

Mine is 2007 has a black top.

old one had alloy rocker cover
new one is plastic

clutch has 2008 marked on it, but rekon thats a replacement....

it may be in by tomorrow teatime

For the manufacturing date try the following (only seems to go up as far as 2004 though although it's probably not that difficult to guess where it goes to at least 2009):

http://www.burtonpower.com/tuning-guides/tuning-guide-pages/ford-manufacture-dates.html