This presentation examines execution and data management strategies used on the Israel offshore Leviathan Expansion Project to accelerate detailed design and support early fabrication readiness. With approximately half of major packages awarded at the start of detailed design, the team leveraged early vendor data to progress engineering deliverables while managing incomplete equipment information through structured assumptions and controlled data substitution processes. The presentation will discuss methods for tracking the transition from assumed to certified vendor data, ensuring design integrity and fabrication alignment ahead of steel release. Attendees will gain insight into how early supplier engagement, data governance, and integrated fabrication planning enabled efficient delivery of multi-package offshore facilities ahead of fabrication milestones.