I'm chasing a manual, though I have thought about doing a manual conversion if I can source it all for the right price. I'm not sold on the 260s as I'm planning on using it for a tow car, and I think they are too nice to be used for that. I'm also thinking the R34 front conversion might be a good project down the track, which I wouldn't even consider on a 260.
I've look at the M35s, apparently they aren't too bad, though I like the thought of having the same drivetrain in the tow car as the track car; will make maintenance a breeze.
Also, as far as budget goes, I'll looking around the 15k mark, but if it's nice enough I may stretch it a little. And if it's in need of work in the right places (ie things I can fix myself) I'm not against saving money.