My understanding is that the "Skylab" module in the Air and Space Museum was actually intended to be launched "wet" as the flight hardware for the Venus flyby.
No, the Venus Fly-by mission never got past the study stage, like many many other proposals of the day. The module on display at NASP is Skylab B, the backup module for the Skylab station and was originally planned to be launched after Apollo-Soyuz to help fill the gap until Shuttle was ready. However there was no budget to build additional Apollo Command Modules which were needed to carry astronauts to the station so the whole idea was cancelled. The wet lab concept was more developed with some mockups built, but when Apollo 20 was cancelled and its Saturn V freed up, the whole plan was shifted to launching Skylab dry and no wet lab hardware was actually built (It would have been substantially different from Skylab module on display)
Two is not equal to three, even for large values of two.