Those IT manuals can be vague. My Oliver parts manual shows 3 seals going on the front of the crankshaft. I only ever remember finding 2. See the attached PDF file for the breakdown. I'd put it back the way you found it. Be sure to soak that cork seal in oil before you install it.

I don't have the IT manual, so the numbers don't help me any. But I don't recall there being anything but the quad ring in the bottom of the housing. I'm attaching an Oliver parts breakdown to show what all is need in there as well.

Since you have a factory shop manual for the 1800, check that out. The steering box should be the same on an 1800C, and the 1800 uses the same front crankshaft seal as the 1650, so procedures would be the same on both.