The System 7.5.3 that Apple made available for download did not have separate disk images. Instead, it was one large disk image in the form of seventeen to twenty (depending upon language version) floppy-sized segments. Under the topic Update Mac OS 7.1 to 7.5 or 7.6, there is a link in the first reply. With the pointer over that link (which now leads to a "not found" page), the directory that contained the files (like E-System_7.5.3_01of19.smi.bin, E-System_7.5.3_02of19.part.bin, E-System_7.5.3_03of19.part.bin, etc) is shown. System 7.5.3 has additional components (such as TCP/IP software), but it will be slower than System 7.0.1 or 7.1 on a 68030 Mac. It also needs more hard disk space.