You're correct of course! Thank you!
--judd
For reference here are commands that work starting from the LONI hdr/img files:
3dcopy icbm452_atlas_warp5_sinc.hdr icbm452_atlas_warp5_sinc
3drefit -view acpc -orient RPI -xorigin cen -yorigin cen -zorigin cen icbm452_atlas_warp5_sinc+orig.
adwarp -apar TT_icbm452+tlrc. -dpar icbm452_atlas_warp5_sinc+acpc.