Hi all. New here. I have a 1969 Plymouth GTX 426 4 speed that’s pretty much original. Beautiful car. Ive had the brakes including the master cylinder and booster rebuilt, fuel system overhauled and many other things done as it sat in a collection for 20 or so years. The issue I have now is a “clacking” noise seemingly coming from the valve train when under moderate load. I had the valves set and no improvement there. I‘m thinking sticking lifter? First, if its a lifter, any hints to free it up? I’m considering having the engine pulled and sent to a good place for a rebuild. If I go this route, any suggestions on who to go to? Thanks, Rick.