You definitely can't user the 5641R with the 5673E without jumping through some major hoops that require the use of external Baluns. The reason is that the 5673E is a direct IQ upconverter that has differential I and Q inputs. So, the complexity of doing that would far surpass the benefit you would get from using that type of setup and there are too many considerations that would very likely come into play during any application development.
The 5663E is possible to use with the 5641R, however, only for certain frequency ranges due to the IF frequency of the 5601 downconverter. For particular RF frequencies the IF if 187.5MHz, but for a very small subset, it's actually at 53MHz. This means you could really only use this combination for RF frequencies that use the 53MHz IF.
There are too many issues preventing this to be a seamless integration. The 5641R works fairly well with the 5610 and 5600 up/downconverters for their entire operating range (2.7GHz).