Has anyone ever done this, wiring the new speaker to the existing board, thus not using the new board with the speaker plug in port?
The 37537 br 120 has no wiring schematic with the parts list that came with it new. This has an early Loksound small black wrapped decoder below the pcb board, and the afterthought tiny sound module wired on. Can it work? If the new 6 pin board must be used, there may not be enough room for the old board, and the decoder, and new speaker. Might the existing large round speaker mounted in the frame work?
Mighht it be better to gut everything and start from scratch?
The existing decoder takes some time to warm up to run it well, and the whistle sound is lame. I bought it new at a substantial discount because someone ordered it and declined when it came in.
I would appreciate the help. I'm fairly seasoned with soldering, wiring, and have installed motors in things that never had any, led's, and resistors. I would rather keep the original pcb in it as the cab lighting makes contact with it, and the pantograph switch is on it's bottom.
So thanks if anyone can advise me.

Thanks HO! I meant to say it has an 8 pin pcb port. The 6 pin decoders were discontinued. I shouldn't try typing in between workout sets, but my gym, layout, and computer are within feet of each other in the basement.

Thanks Bill. Yes it has a condenser but that is on the PCB board and will remain with it. As I mentioned earlier it hesitates until warmed up even on the cleanest track. Otherwise it is a strong puller. No effort to tow six passenger cars and a diner up the steepest grade.