You would be better off getting the SE/30 going first, then you will have a machine that can read/write 800k and 1.4Mb disks.

Once you have that you are laughing as you can get system 7 on the SE/30, then make the 800k disks for the SE.

It's worth checking, is it an original SE, as the later ones have the 1.4Mb floppy.

Another environment for creating 1.4Mb macintosh disks is BasiliskII running on a PC.