I don't think you measured the cam correctly. The rocker Arm ratio (1.55) increases lift at the valve. So using your numbers, .418 X 1.55 = .648, and .356 X 1.55 = .552. I can tell you no stock cam would be that big. Stock rockers can handle a bit over .500 lift at the valve and that is it.
The 1972 Buick V8's were rated at 8.5:1 static compression, and if you measured everything, it is more like 8.2:1. Static compression limits cam choices. The reason for this has to do with the compression stroke. When the piston starts to move up the bore on the compression stroke, the intake valve is still open. It closes as the piston moves up the bore. Since no actual compression can actually occur with an open valve, the actual running compression of the engine is less than the static compression. Different cams close the intake valve earlier or later. That is a big reason why you will see a static compression recommendation in an aftermarket's cam description. Bigger cams close the intake valve later, so they need more static compression. You can read more about this here in the article about Dynamic Compression Ratio.
I would stay with the stock cam. Here (below) is some more information on stock 455 cams.