I completed the tear down of a salvaged 1957 marine 272 with G heads.  I'm curious if the bulls eye pattern on the tappet surface indicates anything?   Almost all of the tappets had these faint circles, some more than others.  Maybe scratches on first start when new?  Unfortunately, the block's water jacket had cracks on both sides but the internals were all very clean.  The camshaft looks good and is 57 spec with the end stamped Z 201. The G heads found a good home and the rear sump oil pan went to a desperate T-Bird owner.  

Those bullseye marks could indicate cranking or starting the engine with minimal or no lube on the camshaft.   That could have happened from the git go or anytime thereafter.  If an engine sits for a long period of time with pressure on the lifter (valve depressed), then there is some bonding trying to happen between the lifter face and the lifter lobe.  Without adequate zinc being already supplanted on the camshaft when an engine is shut down for a period of time, it very possible to get some increased wear at that point.  Excessive cranking of an engine will also do that.
 
Here is a picture of some high mileage Yblk lifters.

Lorena, Texas (South of Waco)

I guess the million-dollar question is can they be used as-is with the same camshaft.