Contrast / Brightness adjust images in Photoshop using Curve Adjustment Layer and gradients

Before bidding, please only tell me about this project only. I don't have time to look at your portfolios. Thanks! OK, now on to work: I have images that are not blending together. I need them to be seamless - top to bottom. Yes, a stitcher will help, but these must be prefect to start with, I need to piece them together without a stitcher. Open all of these and piece them together to see that they do not match in contrast. Next see the attached stitch to see what I'd like the end result to look like, but in separate format. I think that the tops are lighter and the bottoms are darker. When you figure this out, help me implement this process so I can do it on my computer. Images must remain in original format, just contrast adjusted. Attached are samples of the images that I need help with. They all piece together and zipped. ([login to view URL]) Thanks everyone for looking!