Some tips on rear radiators....
-I used thinwall aluminum tubing the first time. Easy to put a bead on, but too thin to bend, leading to more connections. (Bad IMO) Still worked OK for several seasons.
-Second time, I used 1.5" exhaust pipe. You can bend this with your tubing bender. I didn't do any beads to hold the hoses on, but you could with a weld bead around there if you wanted. My hoses without beads, but two clams each, have stayed put no problem for several seasons. A lot of other stuff shook loose in that same time...
-Make sure as much of the tubing is as low as possible in the car. My original setup using the straight aluminum tubing ran almost a straight shot from firewall to radiator. The pipe was at least 6 inches below the highest point, but turns still caused occasional air pockets to appear and made the initial fill a complete bear.
Second time, tubes ran along the floor. Bleeding problems gone.
-You can use any water pump. Obviously, you'd want a better pump for road racing than a street pump, but the point is that any pump makes enough volume to work. I went from a stock engine driven pump to a Moroso electric drive on said stock pump to a CSI electric. All worked fine.
-Put a schrader valve in the lower tube up by the engine. Remove valve when filling until your toes get wet. Then replace.
- If your radiator still has a cap, make sure that one is really high pressure and that the vent is capped so they don't fight each other. I use a Longacre 26# on the radiator and a standard 18# on the front filler, where the overflow is.
Hope this helps. I only autocrossed this car, so I have no input on airflow or issues with wrecking and breaking the tubes.
Because of the volume of water, temp changes are very slow. I had trouble getting my car to warm up enough idling and usually had to drive around the pits to get enough water (and oil) temp.
For a track application, I would mostly be worried about air flow. I think you could be careful with pipe construction and keep joints out of the passenger compartment, which would fix the "getting bumped" problem.