multi-purpose hitches

While I do own a 5th wheel, this question concerns hitches that I use to pull my boats. I have a need for two different hitches, one that is much higher than the other because one of my boats requires a high hitch to allow any rain encountered on the trip to the launch to flow out of the drain hole and one that is about as high as the receiver itself for the other boat. For sometime, I have wanted to get a hitch that could be adjusted high and low rather than continuing to switch out the tow bar/ball each time.

I know that B&W makes such a hitch, but it appears these hitches would rust when left out in the weather, just as my other two hitches have done. I have seen on other trucks a hitch that appears to be made out of stainless steel or some other material that is gray in color (galvanized possibly?), but I haven't been able to find such a hitch online and have never been able to get close enough to these hitches to get the manufacturer's name. The one I'm thinking of has notches all along the back vertical and it appears that all one has to do is pull a pin, slide the hitch up (or down) and then reinsert the pin. From what I can tell, both the ball and hitch itself are made of materials that don't rust.

I know my description is kind of fuzzy, but hopefully I have given enough info for someone to recognize what I'm talking about. Any help would be appreciated.