You would have to be pretty damn dumb in order to put a headgasket on upside down I alwas see people post that s*** and think to myself, what sort of people are working on cars? If it was on upsie down, none of the holes that are cut out on the gasket for water and oil passages would line up lmfao. That s*** is cut so it fits properly 1 way.
It is not common at all for oil to mix with coolant unless you have a blown gasket, cracked head/block. Felpro gaskets are just fine, in fac my dad has a re-used Felpro on his B20 and it runs like a top lmfao. I would take motor back out and have block/head checked again to make sure nothing is warped
BTW Dylan don't take my post as a shot towards you because its not, I seriously see "upside down headgasket" posted about 2-3 times a week on various forums and think, how the hell would someone even do that and not notice it.