The only ABS ones are the original Direct Connection version. And honestly, they’re so thin and flexible I don’t think they’re best. They end up cracked a lot, especially in the screw pockets. Part of that is installation error, but still. At any rate no one is currently making ABS ones, you’d have to find a used original.
I actually prefer the fiberglass ones. MAS made the best one Ive seen, it’s the most accurate to the original except fiberglass. Not super heavy but stronger than the original DC ones. But they went out of business, so again, have to find those used.
The only one I know of being made at the moment is being done by Showcars out of Canada. It's a pretty good reproduction of the original DC spoiler. But the Showcars mold is a little off, the spoiler ends up being a little shorter lengthwise than the originals were. It's not much, maybe a little more than 1/8" per side. It's really just how the lip tapers out on the edge, that particular reproduction cuts the lip off a little flat so the whole thing ends up a little shorter. You end up seeing a little more trunk lid at either end of the spoiler. It's hard to tell, I have an original to compare it to though and you can see the difference when they're side by side
70-76 Plymouth Duster and Dart Sport Showcars Rear Spoiler | eBay