I've got an 86 iroc came with the carbureted 305HO. Rebuilt a 350 etc etc. anyways I'm still using the stock fuel pump. Has two lines. Ones bigger than the other. Want to put in a inline fuel filter. Wondering which is the inlet. I'm assuming it's the bigger one, but want to check before I go hacking. Thanks!

 

Yes the larger is the inlet, the smaller is the return.

But that's not where a filter goes, unless you're just trying to create a new fuel starvation problem for yourself just to prove you can shoot yourself in the shorts that easily. Fuel pumps don't "suck" worth a damn - they suck at sucking - but they're good at pressurizing. The filter belongs on the pressure side.