If you have a 55 cast-iron or earlier Ultramatic, these seals are on ebay:
1875125243 NOS Packard Ultramatic OIL SEALS no reserve! $9.99 1 1d 3h 4m
(CR21164, CR16180 and a small one I can't read)
oil seal - rear housing, oil seal - bellhousing, and throttle lever seal
YFAM, Randy Berger