Pretty sure the standard box is 02J. Not even sure the 6 speed would yield a decent gain even if you could fit it.
 
Surely all 1.8t blocks are the same and you could bolt on a 6 speed leon box?Although it might need different drive shafts and mounts.
 
its not so much the the joints or anything, its the physical size / shape of the box. it just dont fit i believe.
Performance gains from a 6 speed wuld not be noticable, the only benefit would be the 6th gear for motorway cruising.
 
you can fit it. just have to cut most of the chassis leg out of the way to clear an 02M

Quaife do a 6 speed kit.
 
its got to be getting on for double the weight of an 02J... runs different shafts/CV's, wont fit without making a g'box mount.... etc etc

a drop it in job it is'nt.
 
there is a 6 speed version of the 02a/j called the 02s - fitted to some tourans / Mk5 golfs and probably others too