Re: Radiator design?
Put bleeds on both top corners of header tanks. You will want to "y" them together externally and then run a 1/4" pipe back to the expansion tank in the engine room.
I have also run two AN3 fittings from the back of the intake water crossover ports, "Yed" them together and run a line to the front of the intake thermostat bung and then to the expansion tank.
This system will self bleed the entire coolent system and you will never need to burp the system again.
The exception might be the heater core, they tend to trap air. But if you run the heater valve full hot once in a while then it will bleed off any trapped air also.