Oracle® Grid Infrastructure----Installation Guide----11g Release 2 (11.2) for Oracle Solaris
Use "Install GI for Cluster"
As you are already using Sun cluster as a clustering solution, you need to install "Install and configure GI for standalone server" if you are using ASM for your storage solution. Else you may just install the database software on both the nodes, create the database on node and add the database resource to Sun Cluster for the Active/Passive setup to take effect.
Vandana - Oracle