The hoses are 10mm and you can mount a cooler directly in front of the AC condenser, there's loads of room and a good solid base for it, it doesn't need rubber mounting. The cooler in the radiator is very small, about 70mm high and a tad shorter than the radiator. The defunct fittings don't need plugging but it's probably good practice. All you need to do it get some decent hose to make the connections. My local motor factor suggested fuel hose which is what I used. On my current car I just replaced the radiator, much easier and reduces the risk of radiator failure. Personally I wouldn't bother with a cooler, just buy a new radiator and be done with it, it should last many years. Fill with fresh Toyota coolant, job done, takes less than an hour and can all be done from the top.