1950s Cast Iron Slop Sink Drain Options

Our cast iron slop sink has been connected to PVC pipe and taped as a connector for decades, maybe even its entire life. The original tape job failed a couple weeks ago and we’re stumped what the proper way to connect this would be.

There’s no inner or outer threading that I can feel, or any other way I can tell to connect something one way or another. The sink is a double tub that comes down to drain at this point. The two drains connect as part of the entire cast iron tub, so I can’t put something through the top to connect at the bottom to drain.

I can’t find anything online that is a similar set up as this. Any suggestions or can someone point me in the right way for an article or video that might lead me in the right direction? Thank you!