If you're using the crumple zone as your only indicator, then it could still be a hood from 1970. That crumple zone showed up late in the 70 model year. Other things to check would be how the hood molding attaches, and what type of bolt holds the hinges onto the hood.

71 cars front hood molding wrapped under the edge of the hood and had some screws there. Are there holes for these screws?

70 hoods used a used a hinge bolt size that was different than the bolts used on 71-74 cars. (I don't remember the size off the top of my head, but I'm thinking the later hoods used bigger stronger bolts and the holes in the hinges are also larger to accept said bolts.) I'm not sure if the bolt size was changed the same time the crumple zone was added, or if it was done later.

Original paint color/stripes/emblems could also potentially be clues.

Do hoods have date codes???

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