Thomas,
Try as I might, I could not find an MH-37 microphone. The MH-36c should work for basic push-to-talk. The modular microphone/TNC pinout for the FT-2500 is : 1-CALLBUTTON; 2-RX AUDIO; 3-PTT; 4-MIC TX AUDIO; 5-GROUND; 6-+5VDC; 7-UP; 8-DOWN. Good luck in your quest.
Semper Fi,
Tommy - K6YE
DX IS and CW RULES