Help: Writing PRODOS disks from a MAC?

[jrd@hotsprings (John Dunning)]

I've been helping a (mostly non-computer-literate, so far) friend get
his IIgs configured and running.  I've downloaded a bunch of stuff
from various archives, using my mac, and dumped them on
prodos-formatted disks.  The IIgs can read the disks, but when I try
to bootstrap BINSCII, by going to basic and EXEC'ing the BINSCII.EXE
file, basic complains "FILE TYPE MISMATCH".  Other programs complain
similarly when trying to read the files I've downloaded.

A bit of digging reveals that the mac seems to have written files with
prodos file-type $00.  My surmise is that it's supposed to be some
code that signifies a text file.  My further surmise is that the mac
wrote them with a busted file-type because I downloaded them with
Mosaic, so the mac doesn't think they're simpletext files, but rather
Mosaic documents.

Anybody out there got any hints?  Anybody done this sort of thing, ie
download stuff with a mac onto prodos disks?  Please reply via mail,
as I don't normally watch this group.  Thanks in advance for any info.