I'm a bit confused. Are you running the 4 core or the 2 row replacement?
I have the two row aluminum replacement. I referenced the big four row because that is what people familiar with these trucks will recognize. The two, 1" tube aluminum core units were never factory installed, they are service replacements for the old copper brass four row unit. Delco started the trend around 2001 or so. That is when I got mine. I expected a nice Harrison four row factory radiator in the box, but was greeted with this big aluminum Harrison radiator with plastic tanks. The Delco number is (was) a 20978, but it has been discontinued for a while now. At the time, I was very surprised that an aluminum radiator as big as that radiator is could be had for that price. I chalked it up as a win and put it in the truck I was building at the time that later donated its components to the Suburban. If you are on a site with cataloging, use something like a '79 K20 400/6.6L with A/C and A/T as an application and look for a 730 in the part number. For example, I know Spectra uses a CU730 number.
