All coverages and grids: (except the California county boundaries coverage)
This is compatible with GPS data collected in UTM using the NAD83 datum, given the resolution of these datasets. (GRS1980 is not exactly the same as WGS84, but at this resolution, they are virtually identical.)
Some of the grids and coverages had to be reprojected to match the others. The NADCON datum transformation in ARC/Info was used for all conversions. Read the metadata files for details about individual datasets.