The newer Saginaw boxes work, but figuring out the geometry was the hardest part in my build. I needed it for the heavier motor and clearance. I used a mid 70s dodge 4x4 steering box which was reversed rotation and fabricated a bracket to bolt it to the frame. Right now it's too smooth and I personally like a little resistance and "feel" to the steering, so I'll probably end up changing out the regulator in the pump. Really I would only do it if you absolutely have to.

Here's a mock up photo of the setup
http://i131.photobucket.com/albums/...7C-3144-00000126481B60BD_zpse684f992.jpg
Here's the Borgeson joints and shaft I used with a support bearing in the original column
http://i131.photobucket.com/albums/...13-2828-000002C01B3A58A1_zps45bcf9e3.jpg


1950 Chevy 3800
4-53T Detroit Diesel conversion
In the Stovebolt Gallery
More pictures in Photobucket