Batboard

I have a 45W VHF Maxtrac 300 with the 16 pin accessory

Right now I have the pins jumpered to enable the internal speaker-- I want to also have an external speaker installed. How do I do both? I'll end up putting a switch on the external to enable it as a selectable PA.. Can anyone help?

Just wire a SPDT switch to short the two pins 15 and 16 for the internal speaker and switch the external speaker on to pin 16 and switch off the connection to pin 15. The other side of the speaker is connected to pin 1 all the time.
Remember to NOT ground either speaker lead.