65 Barracuda daily driver

If this engine has solid lifters and adjustable rockers, I'd check all the valve clearance settings first. Of course if one is gapped too wide, it will be noisy. Keep an eye on the adjusting screws and make sure that they have the proper drag and are not loose fitting.
(From post 666, I see that your engine has non-adjustable rockers for hydraulic (not solid) lifters).