Due to the engine change, this necessitated a complete redesign of the power systems as well, repositioning all hydraulic pumps and generators onto the engines themselves instead of being fed with bleed air from within the fuselage. The pressurized crew compartment was given a different structure, adopting a very deep glazed front position for the pilot. The landing gear was also redesigned, even implementing a completely different door geometry. An impactful difference was the decision to equip the B-66 with ejection seats, a feature which the A-3 had lacked entirely. Aviation authors Bill Gunston and Peter Gilchrist observe of the B-66 that: "The history of the aviation is sprinkled with aircraft which, to save money, were intended to be merely a modified version of an existing type. In very few cases it actually happened like this... the B-66 is a classic example".