[old Rusty C10]

my buddy says the prestone flush is kinda like an acid and you wanna remove the thermostat and flush it that way , with the heater on once youre done with the flush clean the thing out with fresh water. then use the right coolant which has a silicone base to prevent rusting in the radiator. He did have to change the brackets cause the new radiator is also shorter ,at least the aftermarket one he bought was.he states since they started importing the radiators and make them from different materials the coooling sizes differ and the ports inside may be slightly larger to commpensate for the different size. Double check that the radiator number is the correct one for your truck.
He bought mine from a radiator shop and we have no firsthand knowledge of the ones at advanced. The regular auto parts store he uses ( mom and pop kinda place) had problems locating the correct radiator so he had to go to a regular radiator shop.