I am trying to get this raster file to convert from WGS72 to NAD83, but ArcMap10 doesn't appear to have the correct transformation listed. Where can I find this transformation, and/or how do I import ones that are not already listed as available?
ArcGIS doesn't have any direct transformations for WGS72 to NAD83, so you would have to use two transformations. For WGS72 to WGS84, try WGS_1972_To_WGS_1984_2. For WGS84 to NAD83, try NAD_1983_To_WGS_1984_5 if the data in the US.