How easy would this swap be?

 

do a search, theres a huge thread with all the info at the top of the first gen section

 

Why don't you sell the 3rd gen as a whole and build a nice motor? The work for converting the ECU and the state all that leaves your other car in really does not seem to be very practical.
You could take some of the money from the 3rd gen and build something easier to bolt in that could produce better power. Put a nice sized single turbo and do a good port job. Setup a couple of downdraft carbs and plumb the turbo to it. It would look nicer if done right too.