In our experience this is the best radiator you could put in a Mini for a hot climate. This radiator comes with a fitting for a screw-in fan switch if you are using it on a 91on car or anything with an electric fan. Tested and proven in the summers of the 120 degree summer Arizona heat.
 
The issue with the factory Minis is that they have 3 small cores which really restricts coolant flow. Some people put 2 core aluminum radiators in thinking that it will cool better; but alloy does not transfer heat nearly as well as copper. (Copper is about 40% better at conducting thermal energy than aluminum. Aluminum dissipates heat faster,  but the point of a radiator is not to cool the radiator- it is to cool the coolant!) So the best of both worlds is our high flow 2 core all-copper Mega-Cool radiator. 
 
If you are looking to do the upgrade right, get our complete Mega-Cool kit and save yourself some money!
 
Some modifications to the shroud may be required, mostly oversizing the mounting holes.