263 Oil Pump Question 1953

I have oil pumps from a 1951 and a 1953 263 engine. They appear to be identical. When I pull the cotter pin to release the strainer and tube from the pumps, the end of the tube has a recess that looks like it should have an O-ring or some similar seal on it, but neither pump has a seal. This recess is not where the cotter pin rides. Both pumps worked Ok in their engines. Should there be any kind of seal there? The shop manual doesn't show any O-ring or seal. I put an O-ring from a generic kit that I have on that recess and put it back together. The O-ring I had that fits closest, doesn't appear to be sealing tight either, and it does allow the tube to still pivot freely. I figured the O-ring couldn't hurt, so I left it in and have assembled the engine and dropped it in the car. I'm still hooking up stuff and haven't started it yet. Do you think I'll have any trouble because I put in an o-ring that maybe doesn't belong?

Dave