Noise from engine

exhaust leak should be felt too and possible seen with a black blowby, remove the fan belt and blow some cigar smoke down there to see if it gets disturbed. Id have no issue replacing one lifter with a new one. Break in as usual, just try and make sure its rotating when the motor is running. Put a blob of white out on the edge of the lifter and the pushrod to aid in seeing if its rotating as designed. Id pull the clip and dump the guts onto a paper towel and see if any trash comes out. Just about every lifter I pulled has some glitter in the bottom as its a blind hole, no circulation.