Please remember, If your camshaft was shot, meaning you had a lobe or two that are wiped, or flattened, you would know about it. That engine would be running horribly. If it runs ok, but just has that loud ticking sound and you suspect the lifters, by all means, investigate. A 'ticking' lifter does NOT mean the lifter is bad. It is simply not moving freely within its bore due to carbon buildup (usually). You can gain access to the lifters and work them out as best you can without damaging anything, which I know, is sometimes easier said than done. DO NOT, DO NOT, mix up the lifters, as they must go back into the exact same positions they came out from. After the lifters are out, clean off the carbon 'Ridge' that is present in the lifter bore(s) either by a soft sandpaper or honing stone, again-SOFT. Dont go overboard and use a really course paper or stones. Then, take your lifters, and on a clean work table, disassemble them and clean them very well inside and out with a strong solvent and soft paper. Rinse off all of the solvent. Reassemble the lifters using generous amounts of clean engine oil inside and out, especially inside. Reinstall the lifters back into their same spots. Use new pushrods, they are cheap, dont even bother looking at them, just confirm the length of the new ones before installing them, dont just drop them in. Put everything back together. Change the engine oil and use a new filter. Start the engine. The oil pressure will take longer than usual to build up, This is normal. You may hear LOTS of clicking at first, and this is because your lifters havent built oil pressure yet. After a few seconds, the clicking should go away as the inside of the lifter pressurizes with oil and takes up all of the valvetrain slack-This is why they are called Hydraulic Lifters, no adjustments needed.
If you want to speed up the pressure build-up inside the lifters, then after you reassemble the lifters, put one lifter at a time into an old cup filled with clean engine oil. Make sure the lifter is plunger side up, and is FULLY submerged. Use an old pushrod to push down on the plunger many times. This is called 'Pumping Up' your lifters, and is the proper way of priming a lifter before install. OR, you can simply buy a new set of lifters. If you do this, they obviously dont have to be disassembled, but should still be pumped up before installing. If the lifter set is new, do not worry about which lifter bore you put them in, it doesnt matter and will not hurt the camshaft. The new lifters and camshaft lobes will wear themselves in together over time. That step is only true if you re-use the lifters. All of these steps have been used by myself and many other veteran engine builders for years without failure, we just go with what has worked for a long time.