I will weigh it with all fluids, including 8 gallons of gas, but not me in the car.
As a data point, when I first did the LS1 conversion, the car weighed 1700 lbs with a few gallons of gas. Since then, my wheels are larger and heavier, rear axle is changed (not sure about the weight difference), roll structure is heavier, dash structure is heavier.
On the plus side, fuel tank is smaller and lighter, headers are lighter than the cast iron exhaust manifolds.