There are three options for the headlight reflectors if the silver plating is gone:
(1) Replate with silver as per the original. Problem: They will tarnish over time, so have to be occasionally gently polished with silver polish.
(2) Have them "vacuum-coated" with aluminum. Replicates the silver quite well and never needs polishing. There is a company called "UVIRA" on the West Coast which does this work:
http://www.industrynet.com/listing/1837323/uvira-inc You have to have them nickel plated first. Problem: Much more expensive.
(3) Have them chrome plated. Less expensive and requires no maintenance. Problem: The color is ever so slightly different from the silver.
They're all good solutions, but each has some drawbacks as outlined above. A search through Chevy Chatter will find much more information on this topic. Hope that helps.
All the Best, Chip