Possible to get early A down to 2,700lbs?

The Barracuda is probably at a 150lb handicap compared to a Valiant, just because of the rear glass (and the framing to support it). A Valiant 2dr post would be the lightest setup. The folding back seat probably weighs over 100lbs -- the problem is you're taking weight off the wrong end of the car. But if you're trying to make a limit, you gotta go after the low-hanging fruit.

The narrow body As seemed to use a lot heavier gauge sheet metal than the 67-and-up body, so anything you replaced with fiberglass would be huge. But there might not be much (or anything) available.

The bumpers are another obvious target.