You can use the BlueSCSI Toolbox SD Transfer Utility to transfer files to and from your SD card to your vintage Macintosh.
See the Emulators page for a list and caveats on emulators that support “drive” based images.
CiderPress is a Windows utility that allows you to add or remove files from a HFS image. Runs fine in Wine too.
Old versions of Disk Utility on MacOSX can mount these HFS images if the file extension is