I'm not sure if I remember this right. But the pushrod is case hardened to the same hardness on both ends, but the cam side is a nearly flat surface and the fuel pump side is rounded somewhat. Putting it in upside down will cut a groove in the cam lobe and start scraping material off the fuel pump actuator arm. Depending on the year of the block, the pushrod can be replaced without disassembling the engine. I remember changing one out by removing a plug in the block below the fuel pump and it fell out in my hand. Later 5.7 liters did not have this plug and very recent 5.7 liters did not have a fuel pump boss at all. My 99 Suburban does not have a boss for mounting the fuel pump. When mounting the pump to the engine, it should not sit flat against the mounting boss. An indication that the pushrod is bad is if the pump will sit flat on the boss. The fuel pump has a small amount of pressure applied to the actuator in the at rest position, otherwise there would be a rather annoying tapping noise when the engine was running and the cam or the actuator would fail rather quickly.
To test the fuel pump, ground the coil, disconnect the fuel line to the tank and hold a small piece of paper up to the fuel inlet on the pump, crank the engine and see if suction is present or use a vacuum gauge. Never use you finger, it could be very painful. If there is suction, check the lines to the tank for damage. It could be the fuel pickup in the tank rusted or broke off.
Hope this helps.