With a working System 7.1 on the Performa 450, you should be able to create the bootable Network Access floppy there instead. Use
Disk Copy 4.2 (the Make A Copy button) for this.
You will need a way of transferring the Network Access Disk 7.5, Disk Copy 4.2 and 7.5.3 MacBinary files as they are (do not decode the .bin on the PC). Unless a PC Exchange control panel is in the System Folder, or the Apple File Exchange program can be installed from the 7.1 Tidbits system floppy, the easiest method might be through the freeware utility HFVExplorer (try a Google search) on the PC. HFVExplorer uses Mac-formatted 1.44 MB diskettes (you can reformat normal PC floppies using the Performa).
You will also need StuffIt Expander for Macintosh: A file
here, called MACDISK.EXE, can be downloded onto the PC. Next, prepare an empty PC-formatted 1.44 MB diskette via the FORMAT A: command in DOS or the "Full" formatting option under Windows. Run the MACDISK.EXE program on the PC. Follow the on-screen directions. The result will be a Mac-formatted floppy, including a ready-to-use StuffIt Expander 4.0.1 installer. Install StuffIt Expander. Drag each .bin file onto the StuffIt Expander program icon.
The 7.5.3 files do not require the use of the Disk Copy utility. The (nineteen US) files are, once they have been decoded (one .smi and eighteen .part), placed in one common folder on the Performa's hard disk. Then one double-clicks on the first (=.smi) file to mount the total disk image. The installer will be found in the mounted image.
Jan