NAA 134CI engine

Greetings,
I have saved a mostly original 1953 tractor. I’m assuming all original engine, 12V AC Delco conversion.
All was good and fun until bent pushrods and a valve. Currently don’t have a way to remove engine for rebuild so I am electing to just rebuild the head,valves, seats, guides, springs, etc.
I would like to know when or if I upgrade the original 1/4 diameter pushrods and valve guides to the later 5/16 diameter pushrods, do I or should I replace the lifters/tappets? I have measured, eyeballed, and can’t see a difference in the original lifters and brand new lifters or even some used ones I picked up. I pit a piece of plastigage in both, tapped with mallet, and both were the same width. I am referring to the ball on the lower end of the pushrods where it seats or sits in the tappet, will it operate correctly with the old tappets and the new 5/16 pushrods? If anyone has done this, please let me know, as my concern would be if they are in fact different tappets, maybe the 5/16 would mushroom the tappet receptacle?

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