The vintage Matrix +2 FOR-22 interface card front panel can be reused on a Eclipse Median frame, but you will need to source a replacement rear interface card (part number 7100538) in order to use it. The old rear interface card from the M+2 system is not compatible.
The second option would be to simply use the FOR-22 interface in the existing interface frame as a “dumb” 4-wire port, that is use just the audio pairs routed back to the Eclipse frame / port declared as a Direct 4-wire.
The PIA-32 interface assembly used to convert Matrix +2 interface racks for use with Matrix +3 frames would not be a viable option as the RS-422 digital data stream used in Matrix +3 products is not compatible with the RS-422 Eclipse data stream.
The old M+2 operation, install and maintenance manuals are available to download from here:
http://www.clearcom.com/support/discontinued-matrix-user-manuals