help fix my fuel problem

[fdgay]

i swapped out the 4cyl and put in a inline six. i've put about 150 miles. as i was driving the motor stalled as if i'm outa gas. but i'm not. i looked over things and decided the fuel pump was bad. i replaced with a new one. it run greaqt for about .2 miles then same problem. the fuel return line was blocked off becaues the fuel tank didn't have an inlet to the tank for it. the 4cyl didn't have a return line. is this return line the caues of the problem. it worked great for 150 miles. anyone know what my problem is? any input?