Ah, thanks again gearhead.
I wondered if that big round plug-thing could be the pin, just pushed all the way in. It all makes sense now.
So the picture in the 60 manual still shows a small plug for a then still threaded return inlet. - It looked like a pin sticking out to my inexperienced eye.
This is my first 261.
I definitely will use a filter on this full-flow-filtering engine, as it will be used for longer freeways trips across the desert, once a month.

I also keep the bypass filter on my 235.
It has good oil pressure and earlier this year I capped the oil line to the canister inlet and there was no change in oil pressure.

Running my only two engines with oil filters and detergent oil is an easy decision to make:
I really want to keep them in best condition possible for the longest time without rebuilt.
PCV system is another must have for me.

Thanks for all the helpful info and explanations.
What a great site, been reading for the last couple of years and thought I start muddying the water with me newest 261 find.

When I get closer to the rebuilt, I will have more simple and basic street rod questions, if the archives don't have the answers anyway...