Here's what I have found thus far... I'll add to this post as I find more stuff.
Please keep this thread information about fitment, price and part numbers only, if you have questions, please PM the poster and have them edit their original post about the part number. Thanks
These are all heater core part numbers available at CSK Auto (Checker/Schucks/Kragen/partsamerica.com)
These are all also available as GDO or Ready-aire, I believe the difference is the materials used, brass vs aluminum
Part number is 39-8240
Dimensions:
width not including tanks: 7.75"
width including tanks: 8"
height(tank/core only): 10.5"
height( including tubes leading off at highest point): 13.25"
thickness not including tanks: 1.25"
thickness including tanks: 2"
Price at partsamerica is between $35 and $45, depending on which brand
The fitment on this is interesting. It fits behind the front bumper, but it's rather tight, and the end tanks will not fit behind the bumper at all.
Here's an album of the fitment on my car. http://69.73.145.197/yukonart/2005-02-01/

Part Number is 39-9095
Dimensions:
11x7.5x2(includes tanks, but not tubes)
This would not fit behind the bumper, but I'll be taking some basic measurements this afternoon, and posting my findings. I believe it would fit below the bumper though.
Price is $40-$47

Part number is 39-9076
Dimensions:
11x6.5x2(plus 2 3/4" for the tubes coming off)
Price is $34-$40

Part number is 39-9067
Dimensions:
11.5x6.5x2(add 2" up top for the tubes coming up)
Price is $33-$34
This has by far been the best heater core that I've found to do the job, it seems to have the most volume out of all of them, and I also believe that it would not be hard to run 2 in line below the front bumper, where a regular fmic would sit.

Hopefully this is of help to at least 1 or 2 people.
