Like Joe said, not a good idea. Besides the steering shaft input issues, it would add exsess unsprung weight to an already heavy axle, causing ride and handling issues. The Unisteer might be a viable option, as it essentially mounts where the steering box and drag link reside, and do not mount to the axle. All the Unisteer rack I saw on their site were for pre-war Fords, though, which are faily light compared to the 3500# plus Task Force trucks.
Just wondering, why are you considering putting a rack on the solid axle? Seems uneccesary, as the stock Saginaw steering box is very reliable, the same basic design is used to this day on 3/4 ton and larger trucks, plus many virtally all oval track race cars.
