Looking at the pictures, the passenger side duct is as far towards the center of the car as it's going to go because of that seat bracket. The drivers side looks as if you could move the whole unit towards the pass, side. Get the core out and take it to Napa and see if they have or can get something. If not, radiator shop as suggested above. Finelines may be able to build you something for the undercar? Nice looking 300!