What would one of those older cards be, Mon Mothma?
Look for GeForce 6000 era stuff or Radeon HD3000 era. They'll specifically say that they have "HDTV" output. There's a mini-DIN connector that looks like S-Video but actually has additional pins on it. You'll need the right breakout dongle (it's different between nVidia and ATI and sometimes even some cards have a proprietary one) to get RCA connectors.
I don't think you can actually do this the way that would be the most useful. In the end, no matter if you're using component, composite, or svideo, the card has to be generating an NTSC signal (or PAL), which is 525(625) lines of resolution.
What you would need to do is have the card's encoder outputting as close to this maximum as possible, windows outputting this resolution exactly, then do an integral scale of the game and just live with the resulting boarders around the image.
The component outputs on these video cards made about 3-5 years ago were usually just fully configurable outputs that output in YPbPr instead of RGB. They did not limit you to NTSC/PAL or even things that would be compatible with NTSC/PAL. They were intended for use with HDTVs that supported other resolutions (720p, 1080i, 480p, etc.) and offer those as defaults in the driver control panel on Windows, but most of them will let you pick anything if you dig deep enough. They don't have an "encoder" on them that rescales everything like the S-Video outputs all do. The downside to this for normal users is that you are limited to running these outputs at some resolution that your TV supports, and they did all sorts of software tricks to try to "make that easier" for people. The upside in this case is that if you want some weird mode like 372x288, you can have it. Your TV can probably display such a thing, though you may have to adjust the geometry in service mode.
Some of these things do appear to have scalers on them. They'll rescale everything to the nearest "standard" HDTV mode you tell it that your TV supports. However, most of the ones I've played with seem quite happy to just do unscaled output. The drivers WILL get in your way, so be prepared for some headaches, but the hardware is likely physically capable of what you want.