it's carbon microphone and in fact is not a radio but a console to a radar navy operator.
So the equipment brings a handset and a footswitch, but the operators wants a headset! So if I can change one headset, change the plug I will be happy.
Not a simple change I think.
The carbon mic requres an excitation voltage (the +/- 12v you measured), the dynamic mic does not.
The carbon mic will have a much higher output voltage than the dynamic. I think you will need an amplifier.
The easy solution, modify a headset to use a carbon mic.