The specs from the site:
http://www.permacool.com/Catalog/Cat_page04.html

1012 16,000 to 18,000 GVW
Recommended for medium and full-sized cars and light trucks with occasional light towing.
Coil size: 3/4" x 7-1/2" x 12-1/2"


1013 18,000 to 20,000 GVW
Recommended for full size cars and trucks with regular towing and motor homes up to 28 feet long.
Coil size: 3/4" x 7-1/2" x 15-1/2"



I'd hate to overcool it and end up hurting my tranny. Any ideas of which I should get?

 

I'm running the big one, 10x15 1/2" I think it is with the '6 lines. Works perfect, temps stay about 150*, even when I'm beating on it going down the track.

 

160*-200* is ideal from what I've read.

 

i'm just starting to look into tranny coolers. What made you choose this one over all other tranny coolers. And would it work for a thirdgen that still has the a/c?

 

Just the overall size and quality. The tubes are bigger and the fins are thicker. More surface area. Also b/c they're available with AN fittings. I hate using rubber lines anywhere on a car for any fluids. I would never trust the cheesy coolers from the parts stores. Spend a couple $$ and get a good one.