Originally there was a 2" or so wide strip of tar impregnated material which went it that space. Most of those are long gone from shrinkage and fell out.
I don't bother replacing it with anything since the seal which is screwed to the cowl under the rear of the hood supports that floppy section of the hood if the hood is adjusted correctly.
I have seen hoods which had damage above that bracket. I am guessing that it was due to two things.
Improper hood adjustment, and a gap between the tar impregnated strip. This combination would cause the fluttering hood (unsupported at the cowl due to poor adjustment) to hammer against the tar impregnated strip which has shrunk.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission