Ticking valvetrain noise from fresh engine

It may just be those lifter bores are a little more worn than the others. You said you tried less preload... How much do you have now? It requires pushrods, but have you tried more preload? Aftermarket head gaskets may be a thicker compressed distance than factory, adn all else being equal, you may not have enough preload. I find at least .050 is good with stock type tappets, which is what you have.