During the first fire up, you have to keep the revs up so
oil gets splashed on the cam, and the lifters will rotate in their bores. If the lifters don't rotate, they will rub a lobe off the cam. I have done first fire-ups where it runs for 30 seconds, a minute before seeing a fuel /
oil/ water leak that needs immediate addressing, so shut it down then resume after. Just making sure the first 20 minutes of run time is at 2000-2500, even if that time is split into two sessions or more, just don't let it sit there and idle.
I have never seen a motor break 16 lifters. You have something going on there, and if all your pushrods are new looking, that makes me think it wasn't coil bind, pushrods would have bent. Who's cam and lifters are they? Is it mechanical or hydraulic? How did the cam look?