There were a lot of proposed Saturn variants such as:

Saturn IB/Centaur
Had a Centaur (called the S-V) as a third stage. Basically a Titan IIIE but years earlier.
(L to R)
INT-17: S-IVB and S-II (with HG-3s replacing J-2s)
INT-18: S-IVB and S-II (with 2 to 4 Titan III SRBs)
INT-19: S-IVB and S-II (with 4 to 12 Minuteman ICBM first stages)
INT-20: S-IVB and S-IC (4 and 3 engined version) -- intended as a replacement for Saturn IB to achieve commonality in production.
INT-21: S-II and S-IC. Never flown, but a related variant was used for Skylab.

