I've done this on my old Valiant, and on my Challenger. I have always just mounted them to the inner fender, and so far have never even had one get warm to the touch.
1968 Charger project. I don't have a fender tag or a buildsheet, so it's getting a 440. Help me decide on a color--most everything looks great! (NOT white. My Challenger is white. Need some variety :D) 1974 Challenger 360 2012 Challenger R/T 1991 Dakota 5.2