It’s finally time to replace the steering gearbox on my 68 (302 w/ power steering). Before I shell out gobs of $$$, I see there are lots of affordable gearboxes listed as “manual steering” but with a 16:1 turn ratio, which I’ve always understood to be for power steering cars. Are the PS and manual boxes interchangeable?
Yes. Aside from the tag and pitman arm, there is essentially no difference between the “fast ratio manual” box and a power steering box.
For all rights and purposes all factory-style steering gears for these cars are “manual”. The steering assist is separate from the gearbox.
Have you checked out Rock Auto. That is where I found the best deal, rebuilt by Lares Corporation
BTW, I am kinda surprised that you’re finding “lots” of affordable 16:1 manual gearboxes out there, as fast ratio manual boxes are by far the least common factory variant, and typically rather difficult to find, in my experience.
Steering boxes with tag SMB-K, are an assembly of 16:1 steering box and a power steering pitman arm.
Steering boxes with tag SMB-F, are an assembly of 16:1 steering box and a manual steering pitman arm.
The difference is the pitman arm.
By “lots” of them I meant as compared to gears specifically listed for power steering.