I might have what you need. I do the opposite and convert to Kadee’s. A picture of what you have would help. If the mount for the coupler has been lopped off for clearance. You need the mounting piece. I’ve come across 3 different ones. There’s a line up molded in boss that seemed to change locations in different production runs if you need that piece. The couplers changed over time as well.
They at one time offered what was a truck mounted 2 rail coupler. In the box you got this piece minus the 3 rail mount. So these parts are out there. I have a box of removed parts and may have what you need. In fact I still have a few cars in boxes waiting to be converted. I don’t know what you paid for the car. If you have no local source to buy new trucks. Your looking at close to $40 for new trucks. I’ve seen Atlas cars at shows for less than the price of new trucks. At one point. Atlas changed the truck design. They made the sideframes thinner. Bringing them more into scale. Not a big thing. But on a tank car and the trucks being more visible. They do look better. If you go for new trucks go for the latest version.