You're SOL. I had the same problems, couldn't get it perfect and finally came across a professional classic car body work site. Found out the issue is throughout the years the hood essentially bows from opening and closing and leaves the mismatch against the fenders. There is a video of a guy straightening (de-bowing) the hood using 4x4's and a come along and it works perfectly. Don't waste your time shimming and adjusting, it does not work! Been there, done that. Like you already said, you can slightly loosen the hinges and force the hood up to adjust to the cowl, you can also fudge the rubber bumpers on the fender, but it won't make it perfect. SOL cause we both already have our hoods painted. I learned just to live with it. These cars had a lot of uneven gaps and mismatched panels from the factory, so the only way to get everything perfect is by assembling it, align, grind, weld and then finish paint.