Looking at the picture, I would say that there is not any cost-feasible way to lower the weight much. (Although, if you went fixy with it...). Are you sure it does not already have an aluminum seatpost? That would only save a bit anyway. Light wheels can be bought, but at a pretty steep price. You might be able to drop the spinning weight in half. That would make a noticeable ride difference. But that upgrade would cost hundreds of dollars. And, since no one makes nice modern light wheels for this thing, you would have to respace and redish them to make them work. Plus, probably have to buy a cassette to mount on it.

That bike is probably light enough that you will enjoy riding it at its current weight (assuming it is set up and lubed/greased well) for anything less than serious paced riding.

Now, back to that fixed gear idea. Pull off all that fancy machinery off that beast and you will be shocked how sprightly it is. I have a Fuji Espree with similar tubing I think that I have done that to, and it is respectably light now. Course, with one gear, it really needs to have negative weight to help me haul my girth up a hill.

jim