The proposed Saturn IB-B was to be essentially an uprated Saturn IB using the new MS-IVB-2 upper stage, using the HG-3 engine, developed from the S-IVB and an uprated S-IB-A first stage.
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.