At least with the Floppy Drive, it could have been replaced long ago when the original owner (?) took a pair of pliers to a stuck floppy disk and ripped out the heads. Similarly with the had drive, it may have been replaced too. I remember Miniscribe Drives being used in hard drive enclosures for the Plus,  not on an SE or SE30.

As or the ROM & CPU, this would be one of the few times I say to spray/brush with flux and then reheat the solder joints, while pressing down on the socket.