To my great surprice I found out it is possible to fish out the gearbox number on a GT/E without taking the whole center console off. Last weekend I removed the small leather cover which gives direct access to overdrive unit and pressed a small piece of aluminum foil against the gearbox.
One should know exaxtly where the stamping is located, have long fingers and good knees and plenty of time and good nerves. I think some kind of solid wax would work even better than the foil.
I now have complied full set of numbers for our dear old 3197GT:
engine 988E/62, gearbox 397E, rear axle 341E, bodywork 036.
Best wishes, Kare