I spent some time messing around with Snow, a new low-level emulator for classic 68k Macintoshes. It doesn't support hard-drive images from Basilisk II (the most widely-used 68k Macintosh emulator), so I had to make a fresh, blank hard-drive image, grab some install floppies, and set it up.
I know System 7.5 is the last version of the OS that supported 68k machines (and was a free download from Apple), so I downloaded it. None of them were labelled "boot disk" or "start here" so I tried a couple and the emulator spat them back out every time.
I tried System 7.0, same deal.
Eventually I tried System 6.0, and that worked first time. Turns out, The Macintosh SE did not support 1.4MB ("high density") floppies, only 800KB floppies. Once I switched to emulating the Macintosh SE FDHD ("floppy drive high density", I guess), I could use the System 7.5 disks just fine.
Turns out accurate emulation can have down-sides, too!
https://snowemu.com/