Tapping in cam area

[FrankenCub]

I have a pretty loud tapping in the cam area, front. I have adjusted the lifters loosening them till they rattle then tighten till rattle goes away, then another 1/4 turn. Then tried the way GM has in their manual to take them 1/4 turn every 10 seconds till they are 1 full turn past, the engine doesn't like that. Will shut it down just doing one valve that way. Anyhow, I'm starting to think that the noise may be from the fuel pump pushrod. A friend of mine had that same issue crop up on him once. I'm hoping it's not a warn cam, can't really afford that right now lol.
Is there any actual specs to what length the pushrod is supposed to be so I can measure it ?
This is the factory 307, 86k miles on it.