the 3751084 number is 1973-1974 drivers side E, B body. the other number you have, I'm thinking by the date code, is a 1975. you can tell the 1975 and newer manifolds, as they have verticle reinforcement ribbing on them...like 5 or 6 ribs?? I would be interested in purchasing that 3751084 manifold from you; gregory_m56312@yahoo.com or I.M. me back