Looking great! I love projects like this.
I just tried the HHR deal on my 71 Dart (small block 360) and the fan hit the water pump also. My radiator must have been narrower than yours because it fit my radiator perfect (the four "arms" on the edges actually hung out over the tanks).
I didn't want to cut on the car so I got a Derale 16217 2 speed 17" fan for about $160.00 (about twice the price of the HHR deal). Fits with plenty of room and cools awesome (at least according to the autometer gauge). Supposedly pulls 2400 cfm and draws less than 30 amps on startup. Either way it works on my car, and my car has always run hot.
Just thought I'd post that in case anyone was interested in a different option.
Yours looks great!
Steve