I replaced the raw water pump today and it went really well. For anyone else out there with the later model
Sherwood here and you want to replace it with a "drop-in replacement" Oberdorfer with no modifications needed, then you want Oberdorfer model n202m-908 and buy it from Depco Pump in Clearwater FL, as many others have suggested. Depco was really great. Note how this one mounts to the engine in the photos which is different from other models. The only minor issue I had was that because the Oberdorfer is slightly narrower than than the Sherwood, there was not enough room for the two elbow adapters to spin freely into the holes without bumping into each other. I took some 50 grit sandpaper and a palm sander and sanded one of them down a couple of cm which worked well with the soft brass.
I ran the engine with the new Oberdorfer at the mooring for about 30 mins on the mooring and noticed that the volume of water flow coming out of the stern water exit hole was greater and more consistent. The Sherwood would kind of spit or burp out a big glug of water every 3-4 seconds and there was a steady stream with the Oberdorfer. Maybe the Sherwood had an enlarged prostate?
Does anyone think that it would be worthwhile to rebuild the old Sherwood and use it as a backup or should I just dump it?
Anyway, thank you to those who posted advice to me on this and for your previous posts to others on the same topic. It was very helpful.