Bear in mind folks that the early '72, '73, & 74 400 CID Engines were not "Modifieds" but their own unique engine (based largely on the Cleveland design) just as the Cleveland is it's own unique engine. The rib next to the distributor and the different engine mounts are two ways to tell, another way with this one is to take and inspection mirror and locate the partial vin on the block below the backside of the drivers side head. If it matches the year, plant and sequence number it is the original engine to the car and that would be a 400.