How many CURRENT owners of real '74 360 Duster 4 speed cars on here?

Is it worth it? Only you can answer that.
From a strictly financial basis, absolutely not.
While rarity usually commands a premium it doesn't always equal absolute value.
These cars are no exception.
As a whole they are more desirable than the 1975-76 360 cars, not as desirable as the 1973 340 4-speed cars, and far less desirable than the 1970-72 340 4-speed cars.