There are two different types of MULTIPLEX-GPS Sensors:
the older one (no longer in production):
or the later one:
Both of them work with MSB(MULTIPLEX Sensor Bus)-capable systems only, in most cases only with M-LINK which is the MULTIPLEX 2.4 GHz system. I guess the GPS does not work with Futaba systems (Fasstest/FHSS); Fasstest/FHSS is not compatible to the MSB-system .
So I hope you got just by chance for it won't really help you with your system.