Bob was talking about the new Clusterize report available in the Overlay panel in the AFNI GUI. The last three columns of that report are the coordinates for the peak value in the cluster. Here's an example of that output:
++ Wrote file Clust_table.1D
% cat Clust_table.1D
# AFNI interactive cluster table
# 3dclust -1Dformat -nosum -1tindex 0 -dxyz=1 1 20 dset+orig.HEAD
#Coordinate order = RAI
#Voxels CM x CM y CM z Peak x Peak y Peak z
#------ ------ ------ ------ ------ ------ ------
2137 -2.4 +7.4 +9.9 -6.3 +5.5 +10.5
1715 +4.1 -7.2 +10.4 +2.1 -7.5 +5.1
189 -8.8 -4.5 +8.7 -8.7 -4.5 +9.9
189 -18.3 -7.1 +12.0 -18.3 -7.5 +11.1
79 -2.5 +1.2 +14.7 -3.3 +0.5 +15.3
32 -76.5 -0.0 -76.5 -76.5 -2.5 -76.5