are they crossflows or ford flows. meaning up and down. are they aluminum one tubers or copper 3 or 4 tubers? i think the crossflows would take a few holes drilled int he core support to mount them. the stock ones just bolt right up. you would want a stock one with atleast 3 tubes if not 4 tubes. or rows of tubes i should say. a 390 with a/c takes 3 tubes. the 4x4 390 with a/c takes 4 tubes and mounts differently to the core support.
