I've received some pretty good suggestions and the vacuum idea would be
great except for the location. Since the leak is between the header and the
firewall, I have about 1/4" (maybe 3/8") gap between the two. There is no
way I can think of to get any epoxy up to the offending area to the outside
of the header. I can only see the viable option of cutting a hole through
the top.

Greg