MAS Fiberglass made a universal, bolt on front spoler that was very similar in appearance to the 67-69 Camaro and 69-70 Mustang offerings. While MAS is out of business, it would not be a stretch to adapt either of those with a few mods.

As far as e.t. reductions, I have no first hand experience with a chin spoiler. Since it is pushing air around the car instead of allowing it under it, it may have some impact. A deck lid spoiler, on the other hand, will have a definete impact. My 80 Volare drag car added .2 e.t. after adding the tall, factory style deck lid spoiler. Conversely, adding a sealed hood scoop took .2 off my time.