I have to make a correction about the double pass radiators. There are no issues in plugging like I was told earlier. Just spoke with two radiator companies and they both recommend double or triple pass for my app. Tripple pass requires bigger pump like a 55. No off the shelf available. must be custom 1.25" double row double pass. I also have an option of a 1.25" tube double row down flow. I plan on using a mechanical pump and good flex fan with a shroud. I have a fan that moves a ton of air.