OEM and cheap replacement pushrods often have ends made by spinning tubing against a hardened cup until friction makes it go soft enough to bend and form a half-sphere that is about the same thickness as the pushrod wall. An oil hole may be left as formed or drilled. Aftermarket pushrods are usualllly made by welding a solid ball bearing onto a tube end, then drilling a hole for oil. A spin-formed end will not be as robust as a ball bearing in taking millions of small impacts.
As mentioned, you may have gotten a defective pushrod 50 years ago- Ford made them in trainload batches and statistical QC is not perfect. Just replacing the stock pushrod(s) may not permanently 'fix' things either: I've had stronger aftermarket pushrods punch clear thru the cup formed in stock stamped rocker arms. This is Smokey Yunick's 'weak-link engineering'. Nothing lasts forever.