how can i switch sim card clock signal line betweem two sim cards?
Using analog multiplexer is simple and easy solution.
In the example diagram attached, the two audio source can be two sim cards. SIM-CLK and SIM-DATA can be now shared between two ICs, with the help of one spare GPIO line  used to select between two cards.  



Remember that it's a bidirectional switch, hence the applications are simply vivid.