Yes, one end of the pushrod has been hardened, and it's supposed to go up top where the rocker arm rides against it. GM painted the rocker arm ends from the factory, so if there are any paint marks on the rods, the painted ends go up.
If the paint is gone (most likely), just clean them up really well, and you can tell which end is different. The harder end looks like a different metal has been attached to the end of the rod, it will be darker. The regular end is the same color as the rest of the rod.
I'm not sure how critical it really is to get the right end up...when I overhauled my engine the first time 9 years and 120K miles ago, I didn't know this. I slapped the rods in whichever way I felt like. No problems. However, this last time, I installed them correctly for peace of mind.
Casey
