CGE models are utilized for the evaluation of trade policy reforms, yet they are typically highly aggregated, limiting their usefulness to trade negotiators interested in impacts at the tariff line. Partial Equilibrium (PE) models used for disaggregate analysis lack the benefits of an economy-wide analysis required to examine the overall impact of trade policy reforms. This suggests the need for a PE-GE, nested modeling framework to support trade policy analysis. In this paper, we develop a PE model that captures international trade, domestic consumption and output, using CET and CES structures, market clearing conditions and price linkages, nested within the standard GTAP Model. In addition, we extend the welfare decomposition of Huff and Hertel (2001) to this PE-GE model to contrast the sources of welfare gain among models. To illustrate the value-added of this model, we examine the impact of multi-lateral tariff liberalization on the Indian economy, with special focus on the auto sector, using PE, GE and PE-GE models. The PE model does not predict the change in overall size and price level for the industry well, while the GE model underestimates the aggregate welfare gain due to tariff averaging. It also fails to account for the change in industry composition resulting from trade reform. These findings are robust to wide variation in model parameters. We conclude that the linked model is superior to both the GE and PE counterparts.