The heavy duty radiator was a 4 core and it was two inches taller than the others. The difference in height is made up by lowering the radiator shelf of the core support 2". I know the 64 factory tri-power came with this as I ordered a heavy duty radiator when I bought my car, but I got a refund because it was already included in the price of the tri-power option.
http://www.jimspontiac.homestead.com/Index.html
