600 Holley Double Pumper on a 318
I also agree a vacuum sec. will work much better for your engine. You can use a double pumper on a car with an automatic but you definetly need a pretty good size stall converter. At least a 3000. Then their still tricky to tune.
Either a 600 vacuum sec. Holley or a 600 Eddy. will be a very close match for your engine right out of the box.