I have a set of Oldsmobile 5A Cylinder heads off a running 307. The exhaust crossover has been blocked with aluminum to keep heat out of the intake. The engine was very smooth and quiet. I do suggest having the heads rebuilt as they came off a 30 year old engine. These are a great upgrade not only to the 7A heads on a roller 307 but also late 350s with huge combustion chambers. I suggest having 1.875/1.624 valves cut for maximum performance. I can get them to Atlanta or chicago for $50 or Southern Georgia for free, otherwise shipping must be DOUBLED as FedEx does not like my 110lb packages. They come to you assembled with the factory parts. Dan 815-298-2912