Engine starts then dies...

[Cheyenne350]

Alright guys little help here, 78 c10 LS1 swap just finishing the my fuel lines with brand new Dorman 16gal gas tank and AcDelco 381 electric in tank fuel pump. The engine cranks starts but then dies after a few secs of idle. I cleaned the fuel filter and lines everything good but still same problem so Two things it could be that I could think off and that’s...

1.Perhaps getting a fuel filter/regulator?
2. Not enough fuel in gas tank since I just put $20.00 which was 5gals to get it going and out the garage fill up the rest there... I’m starting to think it’s very low fuel as I write this. Any help would be appreciated thanks..