Okay, it's not the RAM or the ROM causing the video issue (drat!)

It's definitely something on the logic board itself. I have tried swapping out every component that is user-replaceable, and none of it has any impact on the pinstripes. So I guess unless I recap, I'm stuck with one computer that has no sound and one that has a striped display.

Also, I did manage to verify that the boot disks I was making were no good... so I'm back to trying to figure out a way to re-install the OS on the 160MB drive.