Help with 340 compression + cam change

The fact that some are leaking says that some may leak very fast, and that would effect it. My son's 340 had 2 lifters go in <1000 miles from new, and you could plainly hear the worst one (#4, exhaust) in the exhaust note on the right side. It was a definite miss at idle, and even was felt at cruise RPMs as a bit more roughness in the engine.