Pelican Parts Forums - Weird Crankshaft question

I'm in the process of building up a replacement engine for my track/DE 944S.

I bought a used engine with 55,000 on the odometer. Upon inspection, it shows no signs
of significant wear anywhere....totally consistent with an engine with low mileage. So...because
I figured it wouldn't be a bad thing to do, I put the engine on a stand, took off the oil pan (to install
a pan baffle) replaced the rod bearings and was in the process of installing a crank scraper when
I noticed something very interesting.

The crank moves.... laterally....front to back. More than I would expect. So far, in fact, that if I push as far
as it will go to the rear, the #4 piston rod rubs against the back of the block. When I push it forward,
everything is lined up perfectly....even the crank scraper. Move it back....no go.

So...given the low (documented) mileage on this motor....do I have an issue here, or is this normal?

Considering there are not any (ZERO) marks inside the block that would lead me to believe that #4 is
rubbing on the back of the block, nor were there shavings or scratches anywhere else, is there
some explanation for this? Clearly if this was a problem before I got the motor, it would've
manifested itself in some way....I'd see some damage somewhere....right?

Has anyone else seen a similar issue? The engine is in really great shape....I just don't want to button
it up if I'm going to have to replace something deeper in the block. Make sense?