Top line is return, not the bottom.
2013 CC 5.3
81 C10 LS1 project
well thanks guys for trying to help, i just decided for now till im 110% sure of whats what and IF its safe to run with it without going through the radiator to just put it in place of the factory one. took the bottom bracket that held the factory one and trimmed it and fliped it so itd still have the hole for the air temp sensor thingie, and made brackets for the top, just unhooked the factory one and slid the hose over the lines and hooked it up, seems to run cooler than before but i only drove it for 30 minutes and it didnt even get to 150, and its around 90 degrees out.
factory small cooler
hayden cooler
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02 5.3 sierra rcsb,its stock i swear ....