We stock New uppers, lowers, & pads. To install the lowers on a core support that originally had standard radiator you will need to drill out rivet holding it in place then per factory assembly manual directions bend the vertical rear ledge of core support on engine side where pads go down for a 1 " wide area. This allows the longer 4 core lower retainer to fit.
You can find ours on the bottom of the following page.
http://www.gmcpauls.com/radiators.htm
GMCPaul