Are the black arms with bushes the A4 rear subframe?
Have you added engine mount points to them?
The engine is a 4.2 V8 taken from a 98 A8 and coupled to an A6, V6, 5 speed tiptronic box.
I have added a whole rear subframe and suspension from a A4 Quattro which will have to be cut in the middle to accept the transmission, the heavy bracing is to hold the suspension tops as they would normally be supported bu the parcel shelf.
Before I cut the Quattro to pieces I made jigs for the suspension so that I could re align everything more easily.
I have made a cradle for the engine that bolts to the new chassis rails so that the engine and box can easily be dropped out of the bottom of the car.
If the bracing looks too ugly when it gets further down the track I can always cut it out and make something lighter.
Its probably going to get a whole lot uglier before it starts to look like a car again.