Depends how big the differences are
If you expect big more or less big differences you could start by finding files, that actually differ from your main file.
In this little example I take
file1 and compare it against
file2 through
file8:
Code:
#!/bin/sh
for a in $(ls | grep -E 'file[2-8]') ; do diff -q file1 $a | cut -d " " -f 4 >> differ ; done
% cat differ
file2
file3
file5
file8
Adapt it to your case, rename your main file to something unique and grep all other 499 files by a regular expression or put them all into one directory.
Then you got all filenames that differ from your main file in the file
differ for further processing with a more precise approach.