This report lays out the key challenges in linking the EUCalc "core" modules (WP1-5) and the GTAP model (WP7). A conceptual design for interfacing user-defined sectoral lever settings into inputs for GTAP is developed, identifying correspondences between lever settings and relevant GTAP modelling variables, and between EUCalc and GTAP sectoral classifications. The interface designed in this report is necessary for translating the EUCalc sectoral lever settings into compatible data to generate a set of perturbations/shocks mimicking the EUCalc pathways at the aggregated GTAP sectoral levels, in the objective of facilitating the computation of the transboundary impacts.