Has anyone seen a case crack only behind the oil pump?  Should I scrap the engine and find another donor?  It has 125,000 miles but I do not know any other history other than many oil leaks before tearing down to try and reseal engine.

Just marks from the casting process. They're everywhere. Just harder to see on the outside because they're covered in dirt. Ignore them.

+1 What he said ^^^

Edited September 29, 201510 yr by Crazyeights

Okay, the pic just seemed like a deep crack especially with the aluminum chip coming off of it. Power washed the engine, this is the only place I saw that type what looked like a stress crack. Thanks guys!

Yeah, those look like really ugly casting marks. If you wanted to inspect further and even clean them up a bit, buy a couple cans of generic "Oven Cleaner". Can get them at Giant Eagle for roughly $2 a can. Stuff has lye in it and works 10x better than a $6 can of "degreaser". Shake can, spray on, let it foam 4-5 minutes, then rinse with water. It'll eat all remnants of oil, sludge, etc. and make cast iron or rough aluminum look like it did when new. From here, you can carefully sand the markings back if you were so inclined, making sure no shavings or grit entered anywhere it shouldn't. Oven cleaner works excellent on the exterior of the engine too. Like say you had a leaking valve cover and years worth of oil sludge coating the pan, block, head, etc. It'll take it off to bare metal. Be warned, polished aluminum will dull. Also, if you see any actual aluminum flashing hanging on, that's definitely worth removing.

Just wanted to let everyone who paid attention know this car has been running great for a while.  Not really sure if they had been casting flaws or stress cracks but I did tighten two of the three oil pump screws and lock tight them back down. Put everything together and ran with it.  Should anyone be following the post the biggest take away I learned is to inspect the oil pump when you have this stuff all apart.  I read one guy's post somewhere that 40% of the screws tend to loosen up on the oil pump.  Made sense to me, now I'm going to always inspect oil pumps when doing a belt job.  It was also easy to use the Ultra Gray silicone to seal everything back up with the new o-ring in place.