There should be a pretty good amount out there... may not be easy to search for, as rare information tends to be. If nothing else, consider using the code (possibly a direct port, say if you were to use System C?) from emulators, which are very accurate these days.
Those are, in turn, based on arcane knowledge, both hard won from hacking and reversing the real hardware, and from leaked developer documents. I don't know how much of both (I know N64 has a fair bit of both, and that Nintendo is keen to keep that information under wraps, in part due to contractual obligations?). Join a developer board and see what they can refer you to.

The core itself is probably already out there, the 65C816. I don't know if there were any special extensions added for the SNES though. The graphics and IO of course are the hard part.
Of course, an emulator's output will end at the frame buffers (for audio and video), but you might not be doing NTSC output anyway, for practical reasons (i.e., VGA or HDMI for better compatibility these days), so that should be a fine place to pick up from.
Hm, on that note, I don't know offhand if there was any commercial use of NTSC (or PAL) trickery -- that is, drawing pixels in high resolution, of different intensity, to create more colors than normal. I don't know offhand if the SNES's graphics even had a high resolution mode, but I do know it's got plenty of available colors so it shouldn't really be a problem.. (This would only be a concern with respect to producing all the colors the hardware could possibly generate, if it can produce a fast clock at all -- a good example of this is the PC-emulator-breaking
8088 MPH demo for IBM 5150 PC, that uses obscure CGA text modes to produce up to 1024 colors on the NTSC output -- but not on the component CGA (RGBI) output. Because trickery.)
Good luck, sounds like an interesting project!
Tim