Hi there,
You can create a custom component in NI Multisim. Here is a link for you as a reference:
Creating a Custom Component in NI Multisim
http://www.ni.com/white-paper/3173/en/
In your case, you need to find the spice model of the MC33374 in order to simulate it correctly. I've searched this spice model for a while and found a link which contains all of the MOTOROLA Semiconductor of this family. Here is the link:
http://www.datasheetarchive.com/files/spicemodels/misc/modelos/spice_complete/m_ic.lib
In this library file, there is a section for MC33374 and I've filtered this out. I've attached this lib file below.
Please paste the model when you create the component and let me know if it works.
Regards,
Chen_T
National Instruments
