glass plates with high Dmax?
I have an Epson V500 -- like the current V600, limited features and only scans 6 cm wide, but excellent quality and resolution. Older scanners, not easy to find in reliably good condition, are certainly good enough for scanning large format. Carl Weese uses an old Minolta at modest resolution to produce his large digital prints from 7x18" and 8x10" negatives. There is one advantage of the Epson V750 that may be important for dealing with high density range and scratchy glass plates -- it has an IR channel that can be used for noise reduction without losing resolution, and it comes with software for not just the IR but for multiple exposures to handle the high density ranges.
scott