differences gearboxes in a6 2,7 TDI. Help Russian student)

Hi, guys.

sorry for my english, i'm from Russia and sometime use google.translate

i need to install manual gearbox on a6 c6 (4F) (front wheel drive) 2,7 TDI (engine code BPP)

ETKA say me, that there are only 3 species: JMC,FZJ,HVD

http://data.motor-talk.de/.../fzj-2-7-tdi-190319054829699324.jpg

http://data.motor-talk.de/.../hvd-2-7-tdi-7709302113634993828.jpg

http://data.motor-talk.de/.../jmc-2-7-tdi-5283730710523683086.jpg

Please, tell me, what are their differences...

I also noticed that a4 with the same engine gearbox has different gear ratios: 3,625 (29/8) in a4 and 3,875 (31/8) in a6.

Thus a4 with gearbox from a6 will have increased torque.

question 2: is this true? what ...