Well, I just ordered another radiator. This will be my third in like 6K miles. It will probably be my last one, summit said they will give me a refund for it if I want or just keep replacing them.
Looks like I will have to start looking into other radiators. I'm currently setup to fit a big block radiator and honestly I think that it would be more than enough to keep the 5.3 cool. A diesel radiator would cost me twice as much as a BB radiator and $30 more than my Griffin cost. I want to stay to radiators I can pick up at a part store. That way I can warranty it out without having to deal with shipping. That shit is annoying.
My Griffin is a 28x19 core with two 1-1/4 rows. That thing never gets over 190 unless I'm sitting stationary for 10 plus min.
A HD BB w/ AC is 28x20 with four 5/8th rows
Tube surface area is very similar if I did my math right. I don't actually know what I'm doing though.