I recall reading somewhere that the ATARI 520/1040
machines would run with Mac (68000) ROMs inserted.
True? False? Resource?
False. Not a chance.
The STs used the same processor, but the rest of the hardware was very different.
What you may have read about was Spectre 128, which was a hardware based Mac emulator for the Atari ST, which required Mac Plus ROMs to operate.
There was another emulator, called "Magic Hat" that also used Mac ROMs to emulate a Mac using Mac ROMs. Unfortunately, I can't find any details about it, but I distinctly remember it.
Those old Atari STs though, they're getting a bit hard to find, but you've got to love their unique, Commodore 64-like design. Great little demo boxes.
There were a handful of others, too.