Hello Hobo
I have one or two of those flat hoods but please tell me what year you need. As far as I know there are three styles. First is the early '70 that has no crumple zones and no holes for the Plymouth emblem (because in that year the plymouth emblem was located in the grille) The second style is the later '70 that has the crumple zone but of course still no emblem holes and the third is the '71 to '74 style with the crumple zone and the emblem holes.
Judging by your question on the '71 parts I assume you need the third option ?