I should have checked a little more thoroughly. They aren't even close.
But they do bolt right into the computer, of course. The faceplates even swap with the Gateway-specific one, because Gateway apparently uses Lite-On DVD-ROM/CD-RW drives.
The older Lite-On computer drive, the SOHW-1673S, that one has almost identical mechanicals; only the chassis is different. So guess what I did?
That's right: I swapped the SOHW-1673S mechanicals into the DDW-813s chassis. After a bit of problem with the loading mechanism--the DDW-813s uses a belt drive and the other uses gears--I now have it recording a DVD, and in a minute I'm going to check to see if some of the other issues that cropped up months ago are now gone.
The SOHW-1673S seems to be built more robustly than the DDW-813s. For one, the 1673 uses--as I said--gears, rather than a belt-drive mechanism, for its loading mechanism. The optical assembly seems identical in every respect, so I'm thinking that the logic board is what failed in the 813. (I have nothing to base this on, other than blind instinct. But where my instincts are usually wrong about a vast panoply of things, they are usually close, if not totally correct, when it comes to mechanical and electronic devices.)
The 1673 runs at a higher speed when recording, so it makes a nice loud whirring noise. This should only be an issue when I'm sitting here and recording, not when I'm watching and recording.
I could have half-assed the DH-20A3P drive into the DVD recorder, but I decided I liked this method better. Maybe someday I can get an external enclosure and mount the DH-20A3P in that, and just use some longer cables to connect it, but for now this ought to do.
I am tempted, though, to go online and buy a few more 1673 drives, though. But I doubt many are available anymore; I got this one in 2005.
While working on the machine I was thinking about how--in role-playing games, particularly ones in technological settings--there are skills for making that kind of repair, where you take components which were never meant to work together and make them work; and if you're lucky, you can make them work seamlessly.
Which is awesome, of course.