Welcome to the site Stefan.
Maybe check the wheel bearing play front and rear.
Another way to check for runout at the axle flange would be to remove the drums and use a dial indicator to see how many thou the total is. One would have to clean all the rust off and get the correct indicator, If you wanted to check the flange while in gear and the engine running it my be a bit easier to see runout with the brake drum off.
One can have the tires and wheels balanced and still not know if the wheel itself is bent, maybe your tire shop can check the wheels for true.