When working in the Drawing environment (*.idw or *.dwg), the Title Block Swap command from PowerPack for Inventor allows you to define a predefined title block as the current title block in the opened drawing.
The command can be found in the Toolbox panel.

Title Block Swap command
Before running the command, please check the settings to make sure that the correct template has been configured. For more information see Toolbox Settings > Options.