You didn’t need a modded 1541. There was a standard copy program (sorry, forget the name) that could run off of 1 (swap) or 2 (simultaneous) drives; the “modded” drives came much later. None of the drive-only copiers were better, however; rather, they were merely simpler and a bit faster, when making larger numbers of copies. Their success rate was the same, or even a bit lower; they couldn’t match bit density as well as the full version of the program, when that was necessary, for example.
By the by, the 1541 used a 6502 CPU, just like the Apple II and original Atari line of computers. The C64, however, used a 6510, which was a significantly better processor.
