Do both gears and chain. As mentioned stock replacement stuff is not that expensive. I don't know what year they started with the "silent" timing chain cam gear with the nylon covered teeth, but those need to be replaced.
Usually the pitting on the cover behind the water pump, but can also get to the sealing surfaces.
If it is mild pitting, it's not a problem, just if it is so deep as to maybe cause pinhole leaks under pressure.
On installation, use some liquid teflon thread sealant on the end of the bolts. The water pump and fuel pump bolt holes are open to the inside of the engine where fluids (oil) could seep past the threads. Also, most of the timing cover to block bolts are open to the water jacket(s), but that is a bit more obvious when they leak.
On the earlier timing covers, they have a steel bolt on timing tab on the passenger side, and I think the cast iron pump with the lower radiator hose inlet is on the drivers side.
The later timing covers have the timing marks cast into the timing cover case. I think on the driver side (been a long time since I did a small block), with the aluminum water pump with the radiator hose inlet on the passenger side.
All the parts interchange, you would just need to re-mark the crank damper to match the timing marks of the different cover.