I had the same question for the shop that chromed my trees and headlamp. The shop I went with does use hexavalent chrome. I was surprised that they did because I am in California and from what I understand the environmentalists are trying to ban the stuff. You can call the shop if you like. One of the guys in this forum recommended the shop and I am glad he did. The place is called Classic Components, South Bay Chrome. Other people have recommended Browns Plating in Kentucky. There are so many techniques to chrome plating. Everyone has their favorites. Copper, nickel, chrome. Nickel, copper, nickel, chrome etc. etc. I think the better finishes are the ones where the plater puts effort into the polishing process but who knows. These guys have a 26 step process. I doubt Harley has anything near this but I still think they (HD) have good chrome.
http://classiccomponents.com/plating-process