Some variation on what bearings get used in different brands of integrated headset.
have to take the bearings out and measure to have any basis on the compatibility
with current parts specifications.

No, forget threading ... More sensible is complete the threadless conversion,
stem clamps around threadless steerers rather than go inside,
and tightening wedges.

and headset adjustment is only with small allen wrenches, no big open end spanners needed ..
headset can stay, if you can sort out the collar at the to of the top race.

LBS can see what you have , the 1 picture is not as good.