This work provides a methodological contribution to the reconstruction of the seismic design practices in Italian structural engineering of the early 1970s, with a focus on the history of structural calculation methods. The aim is to simulate operationally how an engineer of the time would have approached a seismic design, using limited information, as often happens in interventions on existing bridges. The concept of simulated design developed in this work is based on recreating the calculation environment of the time, using tools typical of the pre-PC era: standards, handbooks, engineer’s manuals, and RPN programmable calculators (e.g., HP67/97) with original codes. Unlike retrospective approaches that use modern tools, this work attempts to "go back in time" by reusing the same logical and computational tools of the era, with compact and transparent algorithms. Reimplementing these codes, through emulators or original hardware, allows rediscovering efficient methods and using them as validation tools for modern structural calculations. In an era of increasing numerical complexity, such historical tools offer a framework of engineering consistency for interpreting results obtained from FEM software. This paper discusses the potential of this approach, proposing the integration of simulated design into the structural evaluation process of existing bridges, while enhancing the technical heritage of the history of seismic engineering.