Here's a post from long ago, I did this nine or ten years ago. I looked at the couplers, nothing special I had to do to these, the real trick was the old William's semi-scale one I did even earlier, that one took some real doing to get electrocouplers installed!
Electric RR Co upgrade for Williams GG1
I just unboxed this one from a few years languishing away in a closet. Still runs like when I first did the upgrade.
I added a simple cab and automatic cab lights and Rule-17 lighting using a little hand assembled motion sensor module. I've since committed a better version of that motion sensor module to a PCB for easier builds.