Is the split pin attached to the frame of the car such that a hole in the truck fits over it? Or is the split pin loose like a kingpin?
I came across an old tank car with a split pin that was attached to the frame of the car. I believe it was an old Arnold product, but I was never able to determine which replacement truck would fit it, but never did figure it out. The issue I had wasn't the truck itself, it was the old style Rapido couplers... I also couldn't figure out how/which MTL coupler might fit if I just wanted to upgrade the coupler in the existing trucks. I ended up just pitching the trucks, cutting off the split pins, and using the tank car as a stationary oil tank in my scenery.
BUt when talking about passenger cars (like yours), the trucks could be very different than the ones I came across.