Gearbox compatability

[wolf1]

Picked up a 98 Audi A6 1.9tdi avant for pennies the other day which needs a new box (was cheaper to buy this than renew the cambelt. waterpump Aux belt tensioner, two tyres and tax my 2.5tdi) .
The original box was a DHF one but I was wondering what the interchangeability of VAG boxes was like. Anyone know what other VAG boxes will slot straight in? Engine is the AFN 1.9