I've heard of as low as 2200ish for a 70-71, but advertised weight is about 2340. Some parts of the body are beefier in 72+, so 72-73 weigh more by a small degree. The rear end location was changed slightly in 72+ also, there was a wear issue in 70-71 that this solved.
With that in mind, I wanted to find a 72+, a few extra pounds are not a huge deal. If you really really wanted a light weight car there are other platforms, I've heard of 1700 pounds 510s (race ready), but hey, were already pretty damn light.
They eventually progress to about 2700 pounds in 1983, now 400/500 pounds becomes a big friggin difference to me, and 2700 isn't that much lighter than a 3000 pound car with 400-500 HP which I could have had with an American car, plus the early years are smog exempt and I like the body style better...