FWIW, it looks original to me. We have an original 70 440-6 in the shop now. The underside of that car's bubble looks like what you have pictured. I've had to re-work way too many reproductions , and none were as defined around the perimeter with centered bolt holes or had the raised bosses centered with the screws. All the repro's I've dealt with had to have the bosses reglassed to shift or raise them in order for the screwed on components to fit decent. And I won't begin to describe the problems with the top sides
of the repro's.