Short answers, pulled from the story.
The Rocketdyne H-1 engine traces its lineage back to captured German V-2 ballistic missiles from World War II. North American Aviation received these engines and converted them from metric measurements to SAE standards to form their Propulsion Division.
Rocketdyne launched their REAP program in January 1953 to standardize on RP-1 kerosene fuel. This specific fuel was officially specified in Military Specification MIL-R-25576 during 1954.
Eight Rocketdyne H-1 engines formed clusters of eight units that served as the power source for Saturn I first stages. These same eight-engine configurations powered Saturn IB rockets during the Apollo era.
The X-1 prototype replaced complex valve systems with valves operating directly on fuel pressure itself. Engineers removed the complicated start tank system entirely and substituted it with a small solid fuel rocket engine that fed exhaust through the gas generator.
Wernher von Braun handed preliminary Saturn design tasks to Heinz-Hermann Koelle in April 1957. The project aimed to meet Department of Defense requirements for heavy-lift vehicles capable of delivering 10,000 to 40,000 pounds to low Earth orbit.