The lifters are probably worn concave on the bottom, resulting in a bell-mouthed condition that will make it difficult to pull them through the bore in the block. If so, both the cam and the lifters are junk. I'd suggest dropping the oil pan and using a long, thin punch to tap the lifters out from the bottom. Then use a straight edge such as the back of a new hacksaw blade to check the bottom of the lifters. If you can see daylight in the middle, pitch them, or have somebody with a lathe and a tool post grinder resurface the bottom of the lifters. There will be a corresponding radius worn onto the cam lobe, which also makes it unsuitable for further use unless it's reground.
Clean the head bolts on a wire wheel buffer and reuse them, no problem.
Jerry
