A couple alternatives here. I have shortened steering arms by cutting and rewelding, done by a certified welder. Some of these cars have seen over 100,000 miles with no problems. I have also done this by building up the steering arm with weld, and redrilling the arm closer to the king pin axis.
Alternatively, you could use a 94 to 97 Jeep Cherokee steering box, a 12 to 1 quick ratio, and a functional bolt in replacement for the Roadmaster box. They are usually $50 at a salvage yard.