how to make find-file treat space/dashes like any other character?

[Thouis (Ray) Jones]

Is there an easy way to configure find-file and its ilk to treat spaces &
dashes like any other character in file completion?

If I have three files in a directory with names:
abc 123.txt
abc-123.txt
abc_123.txt

Completing filenames from "abc" in find-file will preferentially choose the
first, then the second, then the last.  I'd like for it to treat each of
these the same (stopping at "abc" and prompting with a list of completions).

It looks like this might be hard-coded in completion--try-word-completion,
and I've started to try to write defadvice for this function, but am hoping
there is an easier way.

Thanks,
Thouis Jones