AFAICT, Universal used two types of Oberdorfer pumps. The only real difference between them is how they attached to the engine. One (202M-16) needs a little shaft-adapter thing to extend the shaft and is used when the engine has a flange bolted (actually, nuts on studs) on it to adapt the bolt pattern to the pump. The other style (202M-03) bolts directly to the engine: no shaft extender needed. I've read the reason for the two was that back in the hey-day they were building so many engines they bought all the stock of the regular 03 pumps and adapted for the other model just to keep building. The spot it bolts on to is where the hour-meter attaches to on the tractors the engine was designed for. Some engines might be fitted with Sherwood pumps, but even in that case you'll want to replace it with an Oberdorfer.
You can tell which pump you have by seeing how it attaches to the engine. If there's a flange, you'll need the -16 If not, it'll be the -03 probably. Look at the pictures online of the -03 and note the two mounting holes, then look at the -16 and note the 5 mounting holes, and compare to your pump. The -908 model you linked isn't the right part (no mounting holes).
You should be able to get a new pump for about $260 from partsandpumpsonline. When I did my first pump replacement I had them ship both styles since I wasn't sure and the boat was far away at the time. When I replaced my timing gear cover I had to take off the adapter flange and realized then that the other style pump which I had on the bench would mount directly on to where the studs were for the adapter flange and I wouldn't need the little shaft extender either.
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