Maybe you could use the Apo Sironar s 240mm, 300mm or 360?
I'd guess performance is really nice, but those are copal 3 lenses which probably weighs a lot, and the 300 and 360 will require top hat boards due to their long flange distances. I think the weight will be a problem, the Techno is weaker at the large extensions so one need to be careful already with the 180mm to not introduce vibration. The 240mm could work though, but is a bit close to the digital 210. The sironar s lenses are still quite expensive too.
Concerning focal length the Nikkor-T 270 seems just perfect and flange distance is short enough, and only copal 1 and filter 67mm (the sironar 240 has 86mm filter thread, the 360 has 112mm (wow!)), prices are low(ish) but performance will not be as good I guess. Compared to cropping down to 12 megapixels as I have to do know it will hopefully deliver more resolution though.
Another thing I need to consider with these long lenses is that I will probably miss back tilt more than with normal lengths. By tilting the camera and raising the back I can simulate it to some extent though, I think that should be enough to stay reasonably in center of the image circle.