I'll just tell you now this isn't going to happen unless you want to dump at least 500 bucks into this. You'd need at least two iwaki pumps running through this loop to even keep the water moving.
I mean, 30-40 feet to the AC unit, double that and you've got close to 80 feet of tubing. Most loops use probably less than 4 feet of tubing so you'd probably need at least one iwaki for every 10 feet of tubing or so, which will run you up over 800 dollars.
What you're suggesting just simply isn't possible, I'm sorry to burst your bubble. You'd probably recieve just as good of results submerging your rad in ice.
Just to put this project into perspective for you, a $75 MCP650 DC pump has a maximum head of 10 feet.
edit - also just remembered this thing would take forever to fill/empty and bleed