Is there a Vin number stamped on the block by the lower rear flange of the block by the oil filter? Does the intake have a Holley carb? Is there an upper bolt between the ports? Oval ports are usually round or smaller than a rectangular port with no upper bolt. It could have an after market intake on it. The block must have been machined, "decked" to remove the stampings on the pad. It must have been rebuilt some time. You will need to remove one of the heads to make sure what piston dome height. A high dome is an L72, unless the builder replaced the pistons with lower compression domes to run on "no lead" gas. NICK L72