I can confirm that the Tele Xenar is 5x7 only.
For 8x10, you need to go to
Schneider Kreuznach:
Apo-Symmar (240mm and up), a Super-Angulon (165mm and up) or a Super-Symmar (210mm)
Caltar II brand:
Symmetrical (240mm and up)
Nikkor:
SW Series (120mm and up), W series (240mm and up), M series (300 and up), T-Ed series (1200mm)
Rodenstock:
Grandagon (155mm and up), Sironar-N (240mm and up), Apo-Sironar (210mm and up), Apo-Ronar (360mm and up)
This is according to an old 1990's Calumet catalog.
I have no information I can get to right away for older brands like Wollensak and Kodak, but I know they made some 8x10 lenses.
Another option would be to go the DIY route...