Having built countless similar conversions, EBCDIC[1] to ASCII can be as simple as a lookup table and "packed string data" is just binary coded decimal [2] with a sign.
What is a fixed delimited file? A 'mainframe' file is generally fixed length or delimited.
I have used delimiters within a fixed-width file so that I can fit more data in a width field in a fixed-width file layout. This is usually when I have to work with a mainframe, and can't define the layout, of course.