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The Nuclear Materials Identification System (NMIS) detects and characterizes fissile and nonfissile materials using time correlations between a time-tagged source and one or more detectors. The first fieldable configuration of dedicated hardware and software was developed in the 1990s. In its original configuration, the measurement system consisted of a time-tagged source and two to four detectors. Measurements with this configuration were easily simulated using a single Monte Carlo run. The present measurement configuration is far more complex than the original. The source is now divided into multiple neutron cones; significantly more detectors are included; and the source, detectors, and object being interrogated can all be moved during the measurement to capture different views of the object. In addition to the hardware changes, the software can now reconstruct high-resolution tomographs of the 14 MeV neutron attenuation coefficients and fission sites inside the object. This work shows how a complex measurement of an object that consists of both fissile and nonfissile parts can be simulated by using multiple input decks and combining the resulting output into the desired format. The results of this simulation were then reconstructed using the imaging and fission-mapping software used with measurements. These reconstructions are consistent with the original model, thus validating the simulation method.