If you have anough disk to generate a FAT partition to temporarly hold
the unzip'ed ISO then put it there - or maybe put a spare hard disk in
box temporarly.

You should then be able to use the boot/install floppy image which is on the
same page as the ISO at the bell-labs site to start the installer.

It will offer the devices where it thinks the ISO should live and you can
chose your FAT partition; and you are off...

Don't worry if it takes a long time it often doesn't use DMA during install
but you can turn that on later. Alsi I would suggest you do a fossil only
install for now unless you want to build a proper fileserver, again you
can convert later.