It wouldn't be TOO bad as far as N* swaps go. Plenty of engine room. You could use any transmission that came with the 60*V6 pattern with a few modifications.
However I have to say it probably wouldn't be the best engine to pick. A N* is 300hp/295ft.lbs for the Vin 9 version. It would be significantly easier and WAY cheaper to just swap a 500/472 from a 68-76 Caddy, a 500 should match the HP and make almost 200 more ft.lbs. You would give up some mileage though.