And the same goes with the bottom hose.
The Koyorad radiator fits perfectly. Once the covers go back on, we won’t even know the radiator is there, except for the fact that the car should be running so cool.
When filling up the car back up with coolant, you’ll be bleeding out the air bubbles by slightly loosening this plastic nut on the top coolant coupling. The way we did it was to elevate the front end of the car only (because bubbles go up), and to run the car with the heater fully on. Every few minutes we’d loosen this screw and let air bubbles out. We’d continue this process until the only thing that would come out is coolant.
Speaking of coolant, what to use and at what ratio is entirely up to you. The more water you have in the mixture, the easier it will be to cool. But you’ll want some kind of coolant in there for its anti-corrosive properties. If you’ll be parking your car outside overnight in anything close to freezing temperatures, having some coolant in there will also be a safer bet, since you'll only protected to 32F with water alone.
If you think you’ll see temperatures in the teens, then an 80/20 (good to 15F) or 75/25 (good to 10F) water-to-antifreeze ratio will suffice. A 70/30 mix will cover you to as low as around 0F. Even though this car resides in Kansas, where it can see temperatures in the teens overnight a few nights in the winter, it’s always garaged and is only driven on days that are at least 35F. Therefore, in order to get coolest bang for our coolant buck, we went with a bottle of Redline Water Wetter, and about a pint of coolant, and the rest distilled water—which is roughly a 90/10 mix. This will give us the anti-corrosive properties we need, while keeping our engine cooler for higher performance.
UPDATE (Nov 29, 2016): So on the day before the article went live–as well as today, Tuesday, the day after–I had a chance to drive the car around for several miles. It was over 60F the first time. Granted, this is not scientific but it just surprised me that, in both cases, and even when stopping-and-going for over 10-15 minutes at a time, the needle would never even reach the half-way point. With the original radiator, it would, and I had a very low coolant-to-water ratio in that as well. As we can see, the car is obviously up to temp on the oil side, but the head stayed cooler than normal the whole time–just what I was hoping for. In the summer we'll be able to get a real test with digital readouts.