AFAIK all Alfa 16V diesels have oilcooler with thermostat.Yes you can add oilcooler with oil filter adapter plate, but that one doesent have a thermostat for oil temperature.... and that is not the best thing... as it cools oil even when it is not needed or not desired.
If oilcooler is from the same type of car, it is very easy to install it, just replace water/oil heat exchanger with original oilcooler plate from 16V diesel, and install oil coooler in original place.
Only problem could be that some models of 147/156/GT have coil for cooling oil for steering in the place where oil cooler should be.
Sollution for this is to replace the steering oil cooler coil with the steering oil cooling pipes from some other 147/156/GT model. This steering oil cooling pipe comes in front of the A/C radiator.
I am thinking to install this oil cooling modification on my 2.0 TS, since I have oil temp gauge, and oil engine temperature goes to 110-115 C very fast during driving uphill or fast highway driving.
Note that water temperature never goes over 90 C. I have checked the "real" water temperature using OBD diagnostics, and in real world it goes up much more, but AFAIK on 147 (but not on 156) water temperature gauge is programed not to go over 90 except when there is a real problem.
I also think that this high oil temeprature is one of the main problem resulting in failing 2.0 TS engines (right after high oil consumption which leads to low engine oil, and of course broken belts)