'88 Chevy Nova Hatchback (Toyota Corolla)

So, I fixed the leaky front crank seal after a total rebuild. And, I tightened up a loose cam belt tensioner and passed smog tests.

Now, I notice a huge, 1/4" end play in the crank! Is the only cause faulty or wiped out bearing shims on the crank? I suspect low oil from the leaky crank seal (it was massively leaking) may have wiped out the end play shims, yet not affected the mains or rod bearings. Does this sound plausible or likely? Any other thoughts on what to check before I pull the oil pan? Thanks!

Is this a manual transmission car? How many miles on the engine? Not much else to check other than the main trust bearing surfaces and the corresponding surfaces on the crank cheeks.