Here is the process I use for 1-3 story buildings.
1. Open IFC in new PLN - DO NOT CHANGE STORY HEIGHTS!!!
2. Review IFC model stories/levels
3. Identify which stories match yours (if any)
4. Assuming the main story levels are in both models you have something to work with.
5. Re-assign the all the IFC model elements to "live" on the Home stories that relate to your model. You can do this to group selections of similar objects. Make sure to turn "All Relevant Stories..." setting on beams, walls, roofs, etc. to "Home Story only". This will force all the IFC model elements to show up on stories that correlate to your model.
6. Once you have "corrected" the IFC model you can simply publish a module file of the IFC model and then hotlink that module into your model.
NOTE:
In an ideal world you should establish with your team what levels/story heights will be used on the project and make sure everybody plans for that BEFORE model sharing starts. This is an important part of a projects BIM Plan.
matt johnson
archicad since 2004
imac 27, 4.2 GHz Intel i7, 16 GB RAM, radeon 575 4 GB, macOS 10.14.6
imac, 4.0ghz i7, 16gb ram, Radeon M9 390 2GB, OS X El Capitan