I may be wrong but i thought Hydro assist was the early 67 version of power steering? the setup where there is a hydralic ram affixed to the tie rod.. If thats the case i'm not sure what the benifit would be over a more modern 3.5 to 1 ratio like you can get from readhead steering?
http://www.redheadsteeringgears.com/
The axles look sweet, cant wait to see that cab in paint!