Can someone who knows cooling systems explain the various connections on this Mercedes 190E radiator that I'm thinking about using for my car;

On the radiator there are;
2 x 35mm pipe connections top and bottom which I think are coolant in/out.
1 x 21mm pipe connection which at a guess goes to an external expansion tank/filler.
2 x M16 connections, guessing again one for temperature switch for electric cooling fan and one for temperature sensor for temperature gauge.

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The 2 m16s are probably transmission oil coolers, an oil to engine coolant heat exchanger.

Its item 152365524695 on ebay, if that helps.

As said the 16 mm connections are for an automatic transmission cooler