Something to keep in mind as well - I rebuilt a 360 - years ago with a new cam in it. shortly after getting it running, it developed a tick. Thought it was a lifter - Nope - turned out to be a burnt exh manifold gasket, it burned thru a small passage on one part of the gasket, replaced it and the ticking went away. These werent junk gaskets either - fel pro's. Point being to make sure its a lifter and not something else.
One way to check is to run the motor without the valve covers on - I know its messy - and listen to each and feel each rocker arm as it runs, do one side at a time. You'll know when you find it. An Engine stethoscope will help with this too. The adjustable route might be a way to overcome a loose preload as well if thats whats wrong, you'll need shorter pushrods for this set up, crane etc sells them in sets for use with hyd cams and adj rockers.
When and if you locate the offending lifter, I'd pull it out and examine the wear surface against the cam, there should only be co-centric wear circles, no straight lines across the wear surface of the lifter. If there are straight lines - sorry but the cam and lifters are shot, replace them. Usually this happens when the cam is not broken in correctly or the lifters cant spin for some reason.
Good luck with it.
