Fitted a new aluminium rad in my 97 3.9 +8 as it was running a bit hot and got there to quickly when I removed the thermostat housing to put a new one in there was no stat in there to start with ? , I’ve only had the mog for less than a year so no idea why the stat would be removed but it now runs better and temp is as it should be and the new 14” fan brings it down in traffic
As you probably know anyway, the thermostat restricts coolant flow when cold to speed up warming of the cylinder head and combustion chambers. My guess is that a previous owner removed it in a futile and misguided attempt to overcome over heating by increasing coolant flow throughout the engine. Once it’s hot of course, the thermostat should be open anyway.
Your solution of fitting upgraded rad and fan are obviously the way to go.
In the Mini community it's accepted to drill three 1/8" holes in the 'stat base, it doesn't interfere with it's physical operation so the engine will warm up easily, but it allows more water flow, as the 'stat as you know is quite restrictive even when open...If I owned an 8, I certainly would try it
Drop an old one in hot water & you'll be shocked just how little the open area is compared to your general hose diameter
Conversely if you run an A Series engine without a 'stat cylinder 4 overheats
