Good Afternoon, Parker,
If you put your data on the film with India ink, the information will show up as white on a contact sheet. A Sharpie would be much handier, but it doesn't give adequate opacity. Blocking the light for a half-inch strip at the top of the contact sheet makes writing there with a Sharpie a practical solution. ( I contact on 8½ × 11 inch paper, so there's generally enough space for a blank strip at least ½ inch wide.)
One other possibility: Sheets of mailing labels have about ½ inch at the top and bottom, outside the label area, which can be used to print plenty of data. I don't know how easy or difficult it would be to do this a typical word processing program, but I use Microsoft Publisher to prepare my mailing labels. It's just a matter of putting a long, narrow Text box immediately above or below the labels area. That approach, incidentally, also works great for making small-font return-address labels for postal use. A 6 font allows for three lines (name, street address, city/state/zip.); I normally get six such labels in a strip at the top and don't bother trying to use the space at the bottom.
I use a laser printer and sometimes use transparent labels for putting data in one of the between-exposure blank areas of 120 film; usually a sans-serif 11 or 12 font works well on the typical 1 × 2 5/8 label.
Konical