All I can say on the ECP rad is that 2 1" rows of tubes ought to cool a bit better than 3 rows of 3/4" tubes. Also, the core height is a bit better than the 'unknown brand' 3 row in my son's car. On net, maybe 15% better, as best as I can compute.
Being in Texas, you'll be pushing the heat transfer equations pretty hard, so you would be wise IMHO to put in as much rad as you can afford. I can't really say if the ECP 2 row is adequate or not. But, if you have the option to open up the rad support core to accomodate a 26" rad core as AJ did, I would not hesitate one millisecond to do so.
BTW, your hose setup is for the 1970 and later hose arrangement. A 22" or 26" small block rad from ECP has that arrangement. The Griffin 5-00154 22" rad with 2 rows of 1.25" tubes may well outcool the ECP 26".
26" Small Block Mopar Radiator
22" Mopar SMALL BLOCK HD Aluminum Radiator
Griffin Exact Fit Radiator Details for
One other idea if you have the flexibility in mounting is to use a Griffin 2 row cross flow like the 1-55222-XS. I would expect this to outperform the ECP rads. It has the hoses in about the right spots, and has 2 rows of 1.25" tubes for less than half of the price of the exact fit styles from Griffin...like around $275! That is a pretty good cost versus cooling price point. You can also get the same rad with an angled lower fitting for perhaps an easier lower hose connection.
Radiator Details for Universal Fit Racer Part: 1-55222-XS
