i just gave my 69 r/t the alum foil test. this car has the original carb, intake, air cleaner assembly. also the original motor mount brackets and isolaters so there may be some sag. looks like i might be close to 1/2" from hood/ramcharger assembly. i would think that some clearance would have to be figured in due to engine movement. 1/2" clearance seems to work good with what i have but i'd suspect 1/4" clearance would probably be a minimum.