A friend sent me an e-mail that contained information on a box Borgeson is producing. Going to their site you can find specifications and detailed drawings. Figured this might be helpful for those looking into doing a conversion.
I might have misread the article. It mentioned the original boxes used variable pressure for slower response in the beginning and faster response as more input was used. This new box is listed as 12.7 to 1 ratio.
Sounds like it almost returns to manual steering during the highway second stage, or higher rpm variable stage ???.
AGR 4 1/4 turn box, lower rpm is 20-1 ratio
AGR 4 1/4 turn box, higher rpm is 17-1 ratio
AGR 3 1/2 turn box, lower rpm is 16-1 ratio
AGR 3 1/2 turn box, higher rpm is 13-1 ratio
The 20-1 ratio is why the 4 1/4 turn boxes feel so mushy on the highway.
The 13-1 ratio is why the 3 1/2 turn box feels the highway better at highway rpm's.