The eigenstrain reconstruction method can provide residual stress calibration for processing and simulated service conditions for which experimental data is available. The eigenstrain Contour Method (eCM) previously allowed the reconstruction of residual stresses in large components and was partially validated against experimental CMM data, but further cross-techniqu validation is crucially needed. The eigenstrain source distributions from the previous study will be used to fine tune the creep model to predict the residual stress relief during the PWHT of Alloy 740H weldments. Our model can already predict the 3D distribution of the longitudinal, short- and long-transverse residual stress components from as-welded to PWHT conditions, but validation using neutron diffraction strain scanning (NDSS) is a key step needed to confirm its validity.