Questions about a Lundahl & a Sterling ST69

Hi there, new DIY guy here. I was hoping to change out the output transformer in my ST69 with a Lundahl. I've done the switches with ribbon mics no problem, and make the assumption switching the output would be fairly easy. Needless to say, I have learned my lesson.



I grabbed a Lundahl LL1940 (it being the "Lundahl Tube Transformer"). I've tried following the pinout guide given by Lundahl, but to no avail. Any help would be appreciated. Just trying to learn here.