Bad Lifter 305 what to replace?

[Dead Parrot]

To check the push rods for straight, a glass table or mirror is a good surface. A bent rod rolling over the glass will make a rather easy to hear clicking noise.

If you have an air compressor, pull the plugs and blow some air into the openings. Should be enough air to get any bits of gasket to come back out though open valves. IIRC - you mentioned a bore scope earlier. Can use that to check for stuff in the cylinders as well.