A very thorough analysis of the Oberdorfer 202 cooling pumps.
The only question I have is regarding the grease cap fitting. I don't see that part in the exploded diagram you attached. Does this newer 'N' model pump not have the grease cap like the older models?
I ask because I recently replaced our nearly 10 year old Oberdorfer M202 pump with a new pump sold by Moyer Marine that uses bearings for the shaft instead of the grease cap fitting. The pump I used is the MMI 502 pump shown on this page Moyer Marine Atomic 4 Engine Rebuilding and Parts
I found a lightly used one for $50.