Hello! Both the ATD-L3H and ATD-L3H-IV are excellent replacements for your Gamewell-FCI ATD-HL2F. They offer advanced features and improved technology, ensuring reliable fire detection. The ATD-L3H provides standard functionality, while the ATD-L3H-IV comes with additional intelligent features for enhanced performance. Depending on your specific requirements and budget, either option would be a suitable choice. If you need further assistance or have specific questions about your setup, feel free to ask!