70 chevelle fuel lines

[ls6crate]

boy i love this place.my question is on my 70 chevelle i just noticed (i recently bought this car) that i have two fuel lines on the passenger side frame. do all SS's have a return line or did only certain engines have them? i havenet traced them to the tank yet, do they go into the top of the tank? i'm asking because when i was checking my axle codes i noticed two lines comming out of the side of the tank on the passenger side that were blocked off. at least i think they were comming out of the tank, i didn't check real close. another question, my air cond. system unit was removed and in the opening behind the valve cover, on the firewall,is a stamped steel cover over the opening, and there is no blower motor. my question is if i install a blower motor, will i be able to use my heat in the car since that hole is covered? there is a heater core.thanks in advance.