Conversion to manual steering

Just for some preparation, removing the manifold (as you said) will be critical but be prepared to also unbolt your motor mounts and lift the motor a few degrees. While I'm not a talented mechanic by any measure, getting my power steering box out was one of the less enjoyable jobs that I've ever done on any car. It's like the world's least fun, greasiest puzzle.

The power steering box was pretty clearly installed before the engines went into these cars on the production line. :D

Also, while the 16:1 box will make steering in parking lots heavier (it's not that bad), I think this procedure is a waste if you're going to switch to a slow ratio box. IIRC, the power steering box that you're removing is already a 16:1...so while you'll lose the over-boosted feeling of the powered system, you'll also have a less sporty set up by some measures.

Just my opinion.