the heat exchangers are incorporated into the edge of the running boards. that flat area with the traction cuts about an inch wide.
if you dont have a rear exchanger, look for the crossover tube. should be about a 3/4" diameter aluminum tube suspended by a couple of clamps riveted on to the top of the tunnel extension.
most were attached to the edge coolers with a rubber hoses. you should be able to see them going through a flat tab attached to the side of the tunnel with holes drilled in it.