Base circles of these cams?
So, the .581 (valve)lift lobe (.342 cam lift with 1.7's), could have a smaller base circle by about .025 or so than the .558 (valve) .328 (lobe) lift cam.
That's probably not enough to need different length pushrods IF you weren't on the short or long end of the optimum pushrod length to begin with.
"Sewing machine syndrome"?? You mean valve train clicking?

