I've wondered about how hard this conversion would be for years!
I've attached two pictures, one is 2.4 F40 and other pic is 3.2Q4 gearbox, I happen to have a spare 2.4 F40 gearbox that I've used for one of the pictures.
You will notice that although they may share the same internal layout, the starter motor location and engine bolt pattern are different as well as the takeoff box bolt pattern too.
Gear ratio's are different from petrol to Diesel, 3rd,4th,5th,6th and final drive ratio's are all different.
So lets say, we could use the 3.2 torsen twin diff with diesel final drive ring, we still need to find a take off box to fit diesel gearbox bolt pattern.
Rear diff final drive is probably different too between 3.2Q4 and 2.4Q4.
So in short you really need to find a slavage 159 2.4 Q4 (good luck with that
), use gearbox with takeoff box and mounts, front drive shafts too just to be sure, rear diff/cradle, rear drive shafts, rear hubs. Then see if a Brera 3.2 prop shaft will fit, if not have one custom made by someone like recoprop.
Hope this all makes some sense.