It was a long time ago so I'm stretching my memory, but when I first rebuilt my SR I had a local cam specialist (Wades) regrind my camshaft, and possibly the followers too.
Afterwards it had a very nasty rattle like excessive tappet clearances, even though they were correct. I think I concluded that even though I could adjust the tappet clearances right up top, because material had been removed, the followers were dropping onto their little locating screws at the base of the barrels making the noise.