And if you dont have the PKI backup, Use the Makedrop to drop the new certificate and Grc.dat on the client after the reinstall http://service1.symantec.com/SUPPORT/ent-security.nsf/ppfdocs/2008053014333748?Open&dtype=corp&src=&seg=&om=1&om_out=prod
As Sandeep said even if you do not have the backup of the PKI Folder when you re-install SAV server it will create new PKi and GRC and so you can drop them to the clients using Makedrop utility.