[ QUOTE ]
It begs the question, Why?
If there was an S4 in a salvage yard it would have very little left on it!
[/ QUOTE ]
Not if you got there first but yes the cost to do this and the work involved would be immense.
You can do it to both the 6 speed linkage whole is a little tight I have been told for the 1.8T but will fit. You would need every thing to loom, ECU, suspension, trans, clocks, brakes and so on.
Basically all you would be doing is re-shelling the S4, as you need every thing to make this work correctly. The only thing you may get away with is the loom inside the car providing its not a facelift trying to mate with a non face lift any of those combos.
I have a friend with a RS4 engine and box who keep telling me to let him fit it in my 1.8t but I don't have the £6k for the engine and the rest for fitting. I have the rest of the parts as I have an RS4 shell so I would not have to worry about the other parts; its just the cost.