question about blacktop and coolent return

[OpHaScHiLlM]

i just have a few basic questions hopefully someone can answer.
i recently got a "late model 95 blacktop" but it has a skinny o2 17mm??
the person before me had custom everything, he could of put a wrong one on maybe?? not sure, here is a pic of the front of the motor w/ fins


also ? about the coolant return line like which one is it? here are some pics.


there is that line that runs to the turbo that splits from the heater line, is that it? Or thats not it and....

this thing maybe coming down out of the turbo not hooked up to anything??
if it is where does it connect to the other side?
thanks