NASA's unflown Venus manned flyby program would have had three phases. In the first, a standard Block II Apollo module would be used. The crew would perform a transposition and docking maneuver with the Venus ship which was based on the S-IVB stage. Once joined up, they would live inside the ship and test using the engine.
This is my rendering of Phase A. I'm calling the ship the Venus Transfer Vehicle "Armstrong", and the mission Adonis I. Here the crew prepares to blow the SLA panels and dock with "Armstrong."