Moving a database AND changing the superuser

All,
I did a pg_dumpall in preparation for moving one of our databases from
PG7.3 to PG7.4, but I just realized I have another problem: that DB
(which has served us faithfully for some time) was created for superuser
'postgres,' whilst our new DBs use a superuser name that's aligned with
our product. I'm expecting conflicts when I try to restore the data into
a 'new' DB. Am I right, and if so, what can I do? (I know I could just
try it, but the old database machine will be disappearing soon, and if I
need to do a different kind of dump -- per DB, for example -- I need to
know that soonest.)
                      Thanks,
                      Rich Cullingford
                      System Detection, Inc.
                      rculling@sysd.com