Increasing demand for customized products due to customers' changing requirements has led to a non-standardized assembly operation even for the same product. In addition, assembly operations usually require more than one worker, each characterized by diverse capabilities and constraints. Industrial manufacturers need to ensure that both productivity, as well as workers' satisfaction remains in high levels. Toward this end, optimal sequencing of assembly operations can help minimize manufacturing lead-time and prevent excess fatigue for manual labor workers. Shop floor supervisors and managers should also be supported in efficiently allocating the available workforce to carry out these tasks in the most efficient manner, matching each individual's capacity to best fit the task requirements. In this paper we introduce a web based Decision Support System (DSS) for assigning workers to tasks and producing the optimal sequence for an air handling unit assembly line, leveraging values from real-life use cases most commonly associated with the Heating, Ventilation and Air Conditioning industry. The proposed solution showed in simulation to effectuate significant improvement in reducing unproductive time and workers' fatigue and due to its flexibility, task allocation plans can easily be adapted to fit changing requirements of both production parameters, as well as worker capabilities.