I recommend replacing the cam and lifters if you have any concave lifters. They should all be convex when you put a straight edge on them. A little extra money here will save you a lot of money later.

Convex lifters rotate. Concave do not. This is what kills cams and lifters. If the lifter is slightly concave now, expect it to go bad in the future! This can be in 500 milies or 5000 miles but it will happen.

Sometimes you can get away with just replacing the lifter but just make sure the cam lobe is good by using a dial indicator to check lift and compare it to the others. This is preceded by a visual check for cam wear.