Polo 9N Gearbox in 6N2 Car??

[k7aus]

Im looking at various options now that its confirmed that someone may have altered some ratios on my 6N2 1.4tdi polo - 4500rpm = 81mph in 5th gear???

Can a 9N Gearbox of the same code fit an earlier car i.e. 2004 EXB Box fit 2001 Polo that had original EXB gearbox. I know the clutch is the same, but did vw change over driveshaft size or hydraulic clutch?? etc

Was quoted £1100 for a local gearbox specialist to rebuild my gearbox and check ratios etc etc... Bit steep considering it a 1.4tdi, so considering buying a second hand unit.