You can buy these from ebay for the BA BF. Not sure how much you could purchase one from Ford for. www.ebay.com.au/itm/FORD-FALCON-BA-BF-FRONT-BUMBER-LOWER-AIR-DEFLECTOR-NEW-/150657160866?pt=AU_Car_Parts_Accessories&hash=item2313ddd6a2
Awesome write up. I just did this today on mine. It made a difference. As a note, I removed the 2 bolts holding on the water reservoir for the radiator and moved it aside in order to get easier access to the bolt.
Was too lazy to cut the box - Just bought the bottom box and snorkel - Fitted this evening - Took me 15 minutes - Drives alot smoother - Will see the difference after a week of driving