Tom, I see nobody answered you yet. Did you flush it out yet?
I simply jacked the rear end of the car up, disconnected the large hoses at the root end/radiator and let the water run out. I actually also connected my shopvac to them and sucked every last bit of water out. My intake manifold has a bolt on top of one of the water jackets which aids in letting all of the air out. Simply fill through the overflow tank until the water starts coming out the manifold. Also, I disconnected the small radiator overflow hose, in order to let water run through the radiator easily and removing air, until water comes out of this overflow. Once filled, I started the engine to let the air escape and added prestone until I had the bottom of the overflow tank filled. Messy job, but easy enough.
I'm running prestone and water. You could put Evans in it, but it's expensive.
Do a search and there is a good thread on this. I recommend Ford "Gold" coolant, very high quality and good for the iron/aluminum mix on most of our engines.
The shopvac trick will work to get 98% of the old stuff out. You could flush with water a couple of times before refilling if you really want to be sure.
The Evans coolant is really no advantage in a car like this. It does not transfer heat much better (and straight water is the best for heat transfer but...) and we do not need the higher heat capability of large diesels that Evans was designed for.
I'm using Evans coolant in my TR6 that has had a total rebuild to see what happens and how well it works. I say total rebuild because you must insure you remove all antifreeze from your system. That's all hoses and heater coils. I bought 5 gallons through a BMW dealer for $175 including shipping. Costly yes. BUT what drew me to try this coolant was that it has a boil temperature of 375 F and because it doesn't have any water, it will not create the pressure you get from water (steam). No overflow into a bottle. Also it does help lower temp and since it is glycol no internal engine corrosion or erosion is going on. It last for the life of the engine.
Jay Leno has a Utube artical on this and uses it his collection. Worthwhile viewing. No problems so far.
Tom, I flushed and re-filled my CAVGT40 last spring and was worried about air getting trapped in the system. Several Forum members recommended using a device called Airlift II to re-fill the cooling system. Basically the Airlift device pulls a vacuum on the entire system and then you suck coolant back into car. I mixed the anti-freeze with water and put 13 quarts in a large bucket and stuck in the pickup hose from the Airlift. In just a few minutes it sucked up all the coolant into the car.
The Airlift can be purchased for around $70 from various online sources. Worked great, no mess, no fuss.
I live in Arizona and drove the car in 100+ degree weather and the car ran great.
I found that with 50/50 antifreeze mix that the ally radiator slowly gets disolved - you'll get a little leak at the edges of the core that progressively gets worse. Also the inside of anything ally in the system is getting severly corroded. Swapping to the Evans waterless should stop this as there is no water in the system. As it is thicker I was concerned that it wouldn't cool as well as antifreeze - however it seems better if anything having now done several days on track in 33 degress plus heat.