Fixed field mode for plain text files

When editing fixed-field plain text data files...

White space is significant in fixed field data files. Auto-indenting is not helpful in these instances. I require a mode in which white space is significant and will not be stripped, and any indenting help is turned off. Ideally there would be a toggle to wrap lines on-screen for ease of editing extra long lines.

Fixed field data doesn't have comment lines, so embedding comments to turn off formatting isn't an option.

What features exist that can help me here?