408 valve train noise

I run .040-.050 on them and they are usually quiet. From the wear you have, the lifter bores may not be machined into the block well. It's common on Mopars. You also may have a lot of bore wear, which will mean more oil pressure bled past, and more preload required. You don't want more than .002" oil clearance on the lifter to lifter bores or you may have issues like that. If it gets loud again you may want to consider a solid roller and have the bores bushed.