Hello,
If I am understanding your question correctly, I believe that you will want to connect to your EXTCLK connection on the SCXI-1305. The SMP connection on the upper right hand side of the SCXI-1305 is enabled by setting jumper W1 to EXTCLK. Through this you will be able to provide the external clock signal to you SCXI-1141. I hope this helps,
Here is a link to the user manuals:
http://digital.ni.com/manuals.nsf/web%2Fbyproductcurrent?OpenView&Start=1&Count=500&Expand=3.9#3.9
Regards,
Doug