I agree with Alan's response but decided to do just a bit of research.
The 58 owners manual states that the powere seat on the right side adjusts the same way as the drivers seat.
The parts book I have lists 1 or 2 power seat switches. The part number starts with B9S but the revision date is may 1959.
Did a passenger power seat exist for 58 and 59. It appears the answer is yes. This is the sort answer and the whole process needs further review of period lit. and parts books.
I don't remember what the OFS says as that was 10 years ago as Alan noted. Yes there are errors but completing that revision was a 3 year process. We tried our best and of course there was info that came to light after the printing, but the end result was a very informative document put together by humans.
Alan is currently embroiled in the 61-63 revision and running into many of the same issues from the 5860 revisions and I assume many more. He is getting a lot more help on that revieion and my guess is the size will be double the 58-60. Most don'e relizie the amount of original paperwork Alan has ammassed and the effort required to document even 1 item.
Nuff of the soap box.
I will do some additional research on the lit. I have.
Will add that I have never seen a pass side power seat in any 58 I have or have parted out. But this doesn't mean they did not exist.
At least 59's had window stickers so maybe there is still one that has survived that shows the pass power seat.
More to Follow later
Sun Prairie, Wi.