lmc under bed tank help

[cameyer]

So i started installing my lmc under bed gas tank today and need some help. can any one help me with what filler neck to use? the placement
really doesnt matter for now to me i will probably just bolt it to the bed i just really need to figure out what filler neck to use. Would a filler neck from a newer chevy truck work? Also can any one help me with where the other holes in the tank for the vent hoses should go. My tank in the cab only has one line going to the fuel pump with no vents.