Uncheck Maintain existing client features when updating.Both packages can be separately assigned to the same group.
In that screen, select the correct package in the drop-down menu for use with this group (32 bit or 64 bit base install files).
Under Tasks, choose Add Client Install Package.
Select the group with the SEP clients in it, and then click the Install Packages tab in the right pane.
Select the features needed: Antivirus/Antispyware, Network Threat Protection, Proactive Threat Protection.
If a feature set that meets the required needs does not exist, then choose Add Client Install Feature Set.
Click Client Install Feature Set on the top.
For managed clients, the installation features can be modified for an entire group through the Symantec Enpoint Protection Manager (SEPM) (enterprise edition only).