I am looking to determine the correct Grid Shift Binary (gsb) file for transforming data from the NAD83 original to NAD83(CSRS) geodetic datum for the NWT in Canada. I was able to find reference for a NAD83-98.gsb file for this purpose for Quebec, and I believe I saw another for Ontario, and other provinces, but nothing for NWT.
Unlike some other provinces (see list in answer comments). There is no specific transformation from NAD 1983(Original) to NAD 1983(CSRS) specific to the Northwest Territories, or to Canada as a whole. I have used the assumption that the differences between NAD 1983(Original) and NAD 1983(CSRS) are negligible (Figure 2.,Craymer, 2006) for specific areas.
Craymer, M. R. (2006). The evolution of nad83 in canada. GEOMATICA, 60(2), 151-164,433.