Radiator overflow bottle for a 428

I run an overflow bottle just for the reason you describe. I found that even a bit of "vapor" from the overflow would end up making the passenger side control arm rusty. I just used a generic "kit" I bought at Kragen Auto Parts that consisted of a bottle, a wire-form frame that holds the bottle, and the required "gasket" to add to a standard radiator cap. I mounted the bottle as high and forward in the passenger's wheel well as possible...right behind the headlight, picking up some existing screws. Then, I just added a hose connector and short piece of hose to the factory overflow hose to connect to the overflow bottle. It's a bit crude, but works perfectly, is completely out of site (even with the hood open), and can be removed in just minutes leaving no trace.