I had a similar issue on my 49 International truck. I'd hit the brakes, and the truck would turn left. I tried adjusting the brakes to no effect. As these brakes were old drums, and many of the parts were unobtanium, I put a disc brake kit in. Couldn't get the front to bleed. Finally out of frustration I pumped the crap out of the brake pedal. Found a tiny rust hole in the hard line. Not enough to show a leak normally, but enough to not allow the right brake to apply. Something to look for...