They can just be left as you find them, behind the nuts is a very small
separate 'radiator' for the Automatic transmission fluid, which dumps it's
heat into the main cooling system without actually mixing with it.
No water should be able to leak from there, if it does then the rad is
faulty.
A small amount of reddish fluid might still be in there, but don't worry
about it.

Best wishes,
Ken Phillips

Fit it in as normal, and ignore the oil cooler connections. These
connect to a small copper cylinder inside the side of the radiator,
where the transmission oil can lose its heat to the water in the rad.
Providing the oil cooler is not leaking, then no water will come out
of these connections.

The other responses covered it- you can ignore them.

I did this once and connected the two fittings with a short piece of
rubber hose.  This way no dirt would get inside the oil cooler.
Turned out I used the same rad in another car (automatic) a few years
later.  You should be able to buy caps to cap off those fittings,
although at the time I happened to have extra hose and two hose clamps.

Dont worry about them, I presume you mean you have a manual tranny now ?

just fit the rad as it will wok ok no need to cover the threads unless you
wish to use it as a cooler for the power steering maybe .

yup and nothing