When I put all the Crites parts on my Galaxie, it knocked 230 pounds off the car. I thought that was kind of disappointing; I was hoping to lose more. The biggest gains were in the hood and trunk lid (combined 100 pounds savings, including removing the latching mechanism on the hood), and the front and rear bumpers (combined 95 pounds savings, including the bumper brackets replaced with the Crites fiberglass parts). I also used the Crites front fenders, inner fenders, and core support, and those parts saved another 35 pounds total, most of that in the core support. I was looking for fiberglass doors, but I wasn't able to find them for the '64 Galaxie. They would also offer a significant potential weight savings, but of course they'd be much flimsier than the factory doors, and since I wanted to run a stock door panel and window mechanism/windows, I ended up staying with the factory doors. I don't really have a build sheet for my Galaxie, but I'd be happy to answer any specific questions that you may have.
A tenth per 100 pounds is a pretty good rule of thumb for a 12 second car, but if the car is slower than that, you'll pick up less than a tenth, and if the car is faster, you'll pick up more.