This would be likely with many other solid-liftered engines and also factor in the lifter to bore clearance and you have potential for 'rocking' or slapping in each bore - which also makes it more difficult to measure and adjust ( hot and running) clearances. My own Signet had virtually no wear on bottoms or sides of lifters so if not for the broken compression rings I wouldn't have had to disturb it.The slant-6 had flat-bottomed lifters, and as they wore against the cam lobes, they became slightly concave, which results in some of the tapping noise. That's normal wear. These engines were nearly as quiet as those with hydraulic lifters for the first 50k miles or so, but above 100K often had a tapping sound.
The heads are interchangeable between solid and hydraulic lifter engines. the difference is in the pushrods (hollow for lubing the lifters from the rocker arms ... yeah, backwards but it works!), the lifters themselves and the camshaft.Your Valiant would have solid lifters which require a periodic lash adjustment - unless the head on that slant 6 is much newer than the rest of the car.