I have one in my cuda. Made a huge difference in how hot my car got on the street. Mine is a 3.25" core w/ 2 rows of 1.25" tubes. Biggest one I could fit w/o cutting up the core support. It is a direct bolt in too. It wasn't cheap though.

CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax