I am in need of a 1957- 58 manual steering pitman arm.
What year steering box will you actually be be using?. The 57 and 58 Ford steering boxes have different cuts in the pitman arm hole. They will interchange one way and not the other. You can gently file the one that does not fit. It's about a 10 - 15 minute job.
There is no need to buy another pitman arm. If you can search the sight, this subject has been pretty well covered.
Jay