I have a SE with a bad hard disk, 800k floppy, and no keyboard or mouse

I also have a performa 200 with a good hard disk but the SE will not boot from it

can I plug the good disk into a pc SCSI card, boot up read the disk, and access it from a emulator, install os 7 and the SE actually boot from that disk??...

yep

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http://www.instructables.com/id/Install-system-70-software-on-a-classic-mac-using/