To handle the complex and flexible manufacturing of today it is vital to have well functional information systems for the operators so that they know when, what and where to assemble. The current designs of assembly work instructions differ much between companies, but also between plants within the same company. The digitalization trends and initiatives such as Industry 4.0 show the manufacturing industry the advantages to incorporate new methods and tools into their businesses. Even though manufacturing IT systems are designed to be adaptive to product and volume changes, they are still widely characterized by their rigid structures. Making large changes to manufacturing IT systems with comprehensive structures is complex and requires large amounts of resources. Therefore, it is important for the manufacturing companies to make the correct investments. In previous studies, two current state analyses have been conducted with the aim to map manufacturing engineering processes and IT systems producing assembly work instructions in a mass customization context. This paper presents results from the third part of a longitudinal study which focuses on identifying operators’ information needs in manual assembly of heavy vehicles. This third study aims to identify the information gap between the current state and the wanted state by assessing information needs at 13 assembly stations in three plants belonging to a global production network. The purpose is to identify design requirements for future assembly information systems enabling the practical use of the digitalization.