PetDMC-
Emc2 gave you a good run down. I got my ford van heater core at Auto Zone, NAPA has them too.
I am not certain that the copper fins will make a terrific difference in your setup. I totally understand your desire to get the best you can right from the start.
Knowing what I know now (which still isn't diddly BTW. LOL!) I think I would go with an Escort or Chevette heater core. I think I could get temps with those smaller cores close to what I do with this monster I now have. It is 11 1/2" X 6 1/8 X 2". The escort is 9" tall instead of 11 1/2". I think the Chevette is more of a 6" X 6", but I have to check back.
The reason I used this big a$$ core is because (2) 120 MM fans fit on it real nice. I didn't want to build a shroud or pay to have one built.
Also the Chevy Caprice 1975 heater core (same size as mine) is available at Auto Zone for $21.00, or very close to that.
All the cores listed above are brass/copper and have aluminum fins.
HTH
Jim
