If I remember correctly, the radiator was in front of the radiator support for 6 cylinder cars, and behind the radiator support for V-8's.
Virtually all small block serpantine drive setups use the long water pump, but the original V-8's used short water pumps.
I think there's only about an inch difference between the two.
I don't think you'll have any problems mounting the radiator in front....
JA