Rather than post it all up here, take a look at my build thread on our '54.
http://www.jalopyjournal.com/forum/s...d.php?t=137385
Basically, I kicked the bottom of the rad out about 6" to clear the steering box but had to trim the air dam part of the bottom grille panel to fit around the radiator. Check out page 7, posts 128-140 for more clairification.
I've been watching all of the treads with the Mustang radiators but haven't seen one with a part number. I just cut the rad support off at about 18" down and built 1 x 2" tubing mounts with feet on them to go into the original rad support uprights. I have plenty of room and I think I could get away with one of the Summit or Mustang aluminum rads next time (I've got 4 or 5 more of these trucks, 2 are '54s).