the gas crossover line for our 49 was clogged with old gas that turned into tar, so we filled it with penetrating oil and set it on fire.
Here is the fitting that screws onto the right tank.
Check out the goo that came out of it.
Here is the other side. I wasn't really sure how this would work. The heat pushed the gunk out of the holes. I wouldn't want to use a big torch, it would discolor the metal. My dad went over the line with an sos pad, and all of the original cad plating was intact.