Not noticed this before now, but it must have been mentioned:
http://nfggames.com/forum2/index.php?topic=3083.0
Pal N64 with IC for an RGB amp in place. The same RGB amp as the SNES 2 in fact, and the same VDU as first gen NTSC N64s...
So you could steal the RGB amp from a SNES 2 and get 'proper' RGB from an NTSC machine, or at least confirm what the RGB amp needs to do, which that thread looks at. Might be interesting, I always meant to go back and add an RGB amp to get back s-video on mine.

My NTSC N64 is RGB modded but suffers from the flickering.
It can be sorted with something being done to the cable apparently, infact Charles over at NTSC was sorting me out I think until I went crazy over our cab...
That looks like an ace forum man, cheers for the heads up. With me becoming more confident with a soldering iron now I might have a bash at re-modding it. I have nothing to lose really in trying as I wouldn't get much from selling it. I'll just have to make sure I'm properly done with Ogre Battle beforehand incase teh shit hits teh fan.
I think the flickering comes from shorting some points on the board, rather than lifting pins or fitting an RGB amp. You probably need to change the RGB mod to one of those. Pin lifting is easier and looks fine but disables s-video, and makes the VDU chip more susceptible to static and hot plugging death (not to mention pin snapping while you do it). The amp is more awkward, but slightly safer long term, and you keep s-video. Both will probably look slightly duller, as that shorting method is overly bright I think (also causes interference on whites/bright colors).
Saur is your bona fide expert with this though.
I need to read more about the Nintendo RGB amp IC, but hopefully someone has managed to figure out an exact equivalent circuit rather than all the vague variations floating around. In which case I'll probably go that route when I finally get round to playing Sin & Punishment.
I already have this mod... The guy who did it is trying to get hold of a bulk lot of RGB chips to send out to people wanting to do the mod so that people don't start molesting SNESs.
Pic here: http://ntsc-uk.domino.org/showpost.php?p=1690602&postcount=3334
It looks all kinds of amazing on my plasma.
Also, it's the same RGB chip that was specified for the Ultra64 devkit (SGI thingy?).
I started off with the solder bridge amp, but got the flickering.
Then I removed the bridge and got an amp built in the scart lead. This looked good on my CRT, but my Plasma and my Dad's top of the range Bravia LCD both failed to display it well, with some weird cross hatching that I still can't explain.
This mod has finally sorted it.
Ooo I have a Indy SGI devkit, I wonder if its hanging around on the n64 board that's in there.
That would be a bonus, I haven't got the patience or motivation to break into the OS on that thing.
OK sorry I'm now mega confused. What's the ultimate setup then? Do I still need to get a JPN 64 or can I now mod the shit out of my PAL unit and get the real deal?
What I want is 60Hz RGB and multiregion...
I have a spare dead superfami kicking around and an old SNES...
You need an 'early' (pre-1998?) NTSC-U or NTSC-J machine with the VDU chip, or perhaps a first revision SECAM machine.
Realistically, only Rare zealots go for an RGB modded SECAM model, as it is generally thought the Rare stuff was developed primarily for 50Hz.
So the ultimate setup is still an RGB modded NTSC machine with the tabs removed, and a PAL machine or Passport cart (not 100% compatible) for PAL stuff (though personally - I wouldn't bother with PAL N64 stuff at all).
How you RGB mod is up for debate - from what I understand only very late SNES models and the SNES Jr. has the RGB amp needed, so it might be hard to find one. It is just a simple video amp, so in theory some of the more recent RGB amp circuits posted for the NTSC N64 should be just as good.
Ta Love. I really need to dump my PAL 64 stuff and get that sorted. it's low down on the todo list tbh. Current objective is a 60Hz switch for the Master System.