i was doing a little internet surfing and found this site and thought it might be useful to guys with N/I trucks. it has prices posted. even their lrgest one is not very big but you can get them thick and i'm sure they make up other ones. these are just Air to air coolers. they make all kinds but I was looking for a unit for a 91 N/I and found this site. crossy
http://www.bellintercoolers.com/pages/AAAssm.html