The brute force approach is to copy the dataset files. However, you say that you can't do this because of disk space. (BTW, AFNI can simply read the .hdr/.img filepairs nowadays, so you may not need 3dANALYZEtoAFNI anymore -- that program is a relic of the days when AFNI itself didn't grok ANALYZE format.)

The subtle way is to use Unix symbolic links. Suppose that ../fred/elvis is a file that you wish were in the current directory, but can't mv or cp it for some reasons. You can (in the current directory) issue the command
ln -s ../fred/elvis ./elvis
and this will make a symbolic link in the current directory (./elvis) to the actual file in the other directory. (It is legal to name the link something different than the original file, but that can be confusing.) So if you now create symbolic links in the current directory to each AFNI dataset you want to pretend is here, you would do something like
ln -s ../fred/elvis+orig.HEAD ./elvis+orig.HEAD
ln -s ../fred/elvis+orig.BRIK ./elvis+orig.BRIK
et cetera.

Hope this is clear enough. When you rm the symbolic links, you don't remove the files themselves, just the links. If you rm or mv the files, the links will no longer point to the correct place -- the jargon is that they are "dangling".

bob cox