i/p o/p impedance for conducted EMI filter on PCB

Hello all,
I am trying to build accurate simulation model for EMI Filters used on Mixed Signal PCB in order to predict level of conducted noise attenuation.This conducted noise is due to electromagnetic radiations in industrial environment on data and power lines, which is modeled as current clamp in lab (IEC 61000-4-6 Standard). Can anyone help me with input and output impedance values to be used along with noise source as voltage source in PSpice? Although 50 ohm system is generally used to judge filter`s performance, unlike communication line filters, typical industrial environment hardly provides 50 ohm ip and op impedance. I/p impedance should be low and output impedance of order of Mohms ( i/p impedance of typical OpAmp, as they often follow EMI filters in our design). Is my judgement correct?
Also help me with modeling noise source for current clamp with 150 dBuV strength signal. Currently I am using 1 Vrms V source wrt ground in PSpice to model CM noise. Wont there be effect of Shield on actual voltage induced on cable due to current? How to calculate that?
Thank you.

In most cases, circuit impedances involved with EN 61000-4 conducted EMI (150 kHz..80 MHz) are maximum kOhm rather than Mohm. Unloaded EMI filters may occur in a few cases.