Dave I see the scan is more to comply with print house request.
I too have to comply with print house requests, it’s one of the few times I use j peg
Can you tell me what software you have. PSE can convert to 8bit canons own raw editer can batch process to 8 bit
I would save a copy of what you have now, convert if you can to what they request and save that j pg as a print only image.
I keep a separate folder for such files, so that I don’t make the error of trying to rework or re save
As you have gathered for me j peg is end of the line for a pic
Hope this helps and that I have understood your need