Cheap tube and fin tranny coolers can be picked up from Craptire or Wallmart. Lots of different GVW ratings to choose from and under $100. Not cheap enough for your stingy-arse? Go to PNP and grab one from the myriad of 3/4 to 1 ton trucks. Most of the grills are busted and you will have a lot of room to remove them. Should be a whopping $15 there.
HTH