Jim, From my experience, keep all you can until the car is done. An example on mine, though not the only one, was the spacing of the bolts on the bottom of the front fenders. I'd replaced the sills, and did rust repair on the fender bottoms. I had unfortunately thrown out the old sills, but fortunately kept one of the fender bottoms for some unknown reason. From that I was able to drill the holes in the right pattern. I had to guess on the front of the rear fenders from pictures of other cars and the anderson restoration guide. It worked but was much more trouble. So bottom line is it helps to have a reference to originality when possible, so keep everything until the car is done if space and wife permit, it will save you time in the end.
Hope this helps,