Your 70 impala likely has a 350 V8. the fuel pump is located on the front side of the engine. Follow the fuel line down from the carb to a diaphram looking thing with a line coming from the fuel tank and a line going out and up to the carb. to remove the fuel pump you need to probably gain access by removing the alt. or AC compressor (don't disconnect the lines if they has freon in them, just leave the line connected and lay it over to the side) once you gained access or can get to it without removing anything in your road. you will disconnect two or three fuel lines (some has a return line which is the third line)(can't remember if 70 model had that style) you want to make or note where the fuel lines was connected (usually the metal line will only go one way, but noting where they go removes any dought?) now with the fuel line disconnected you will have two mount bolts that hold the fuel pump to the block of the engine. remove those and the fuel pump is off. Now clean the block so the new gasket will seal (if it don't seal you will have a vacuum leak and if bad enough the engine will not idle or idle funny) the fuel pump runs off a cam lob so some resistance maybe be felt when trying to bolt it back up you can either force hold the pump to the block while starting the bolts or rotate the engine so the lob is not pressing agains the lever of the fuel pump. once you got it bolted up hook up your fuel lines, start the car and look for leaks (ESPECIALLY FUEL LEAKS) no wetness or dripping is alowed. also the engine die a couple of times till all the air and fuel gets pumped up and in to the carb. Now things that might be something else. I would first remove the fuel line at the carb., get you a catch can, remove the coil wire so the carb won't start up. spin the engine over with the starter. fuel should be pulse pumping into the container? if so the fuel pump maybe good. I would then check the filter in the carb and see if fuel is going into the carb. If no fuel is pumping or weak or spitting fuel the fuel pump maybe bad or the cam lob is worn and not moving the fuel pump lever thus not creating the action on the diapramn and not pumping. when you get the old fuel pump off you can connect a rubber hose to it and blow if you hear of fell air excaping out the other connection the pump is bad, is so you may want to change you engine oil cause fuel may have gotten into the crankcase by means of the bad diaphramn of the fuel pump. Rc.