The (yellow) dichomate that you are referring to is a procecess done by a zinc plater.The silver (clear) is another zinc plating. It has been my experience that has great results. I have taken boxes of stuff to my local (PHX)plater,and the cleaned and plated stuff comes back looking great. The cost is relativly cheap. You just have to have a zinc plater near you. This is a common industrial process, and is not related to commom chrome plating shop.
Question in this line. Were the carburetor bodies plated, with silver (clear)? I know the parts assembled to the bodies were plated in yellow.