When replacing water pump on Chevy 4.3 L engine how much antifreeze do you need to fill?

well i have a 4.3 v6 what I did ,was pour a whole gallon of antifreeze in the radiator after I secured all the clamps,then fill it with water ,make sure to remove tools,rags etc, from around engine and radiator,start engine and let get to normal operating temp.add more water in need it,then put radiator cap back on,check for leaks,if none test drive it and then check for leaks again,check temp gauge if have one,let cool down and check water level in radiator again,if everything ok you done,make sure you use the proper type of antefreeze for your vehicle and use proper precautions when handling chemicals and proper ways of disposal, hope this help.