I'm not trying to talk you out of a new finish, but plating a stainless gun with hard chrome is a bit redundant. It does resist corrosion slightly better but not enough to matter unless you're really exposing the gun to a tough environment.
I've had half a dozen handguns HC plated but they were all originally blue and I wanted something more durable.
I've also had a few handguns Cerakoted and it's the best of the "applied" finishes IMO, plus you have your choice of many colors.
Two sources I can recommend should you not already have someone in mind:
http://www.apwcogan.com/ (all types)
http://www.carolinafirearmcoatings.com/ (Cerakote only)