Operation "is this a proper 70 key cylinder"?
This cylinder will not lock into place in the steering column housing. The detent you see there seems to be too big to go into the locking hole of the steering column housing.. Or, is the steering column housing incorrect? The hole of the housing is smaller than the extent on the key cylinder.

Early column collars used a cylinder with a spring loaded blade interlock, rather then the button you show. There was still a hole on collar to depress this "blade" but it's smaller. I believe I had once enlarged that hole to fit cylinder you have.

Correct, the earliers cylinders is actually a 1 year only setup for 70s, pretty much like turning switches, althought these were extended up to first 71 half.

Great picture !!!!
I have the one on the left, so maybe I can just drill out the hole in the housing to allow the detent pin to extend into the hole so it locks properly? I guess if my detent pin style won't lock, then my friend's car is a detent blade style. So either need to get that version of the cylinder or drill out the access hole to allow pictured-style detent pin to protrude into the hole and lock as needed.

Just about all ign. cylinders you see today are the later year types. If the holes are in the same location, just drill out to fit. Just makes it easier to find a new cylinder. Just that it "clicks" in securely & turns reasonably free.

Something else to keep in mind. 1970 only switches are satin chrome finish .....where as modern replacements (aka 1971 and later ) ate bright chrome finish. )
That is if final appearances matter to you.

Quite Right: Not that obvious until you see them side-by-side.