Oh man, that sucks, kinda like seeing your harmonic balancer wobble while the motors running.
The good news is you have a great trans, SDP twins and duel fuelers to go with your new built motor. :hug:
I know of another way to drain the radiator that is even faster. You can pressurize the coolant so much that the end tank of the radiator explodes. My boss did it in SS semi final round at the NHRDA World Finals. Here's a video of the run and a picture of the radiator.