Hi-

3dClusterize doesn't really know/care about the space of the dsets: it will just make clusters in the space of the input dset, and output them in the same space.

In AFNI BRIK/HEAD files, there is the "afni view" part of the extension: +orig, +tlrc, ... and a couple others. This is definitely confusing, but the "+tlrc" doesn't literally mean Talairach-Tournoux coordinates specifically-- it just means "a standard space". So, even if you have data aligned to MNI space, those dset extensions will include "+tlrc". (This goes back to the eeeearly days when there was just TT as the standard space-- but now standard spaces have *greatly* proliferated.) This AFNI view somewhat mirrors the NIFTI_XFORM_* encodings.

--pt