71 Duster 318 fuel pump not pulling fuel from new gas tank

I won’t know if the lock ring is good ‘till I get more gas in the tank. Either way - the fuel pickup line should be submerged with 5 gallons in the tank. For the record - the lock ring was very unsatisfactory because the diameter is too small to center reliably. I actually had to pull the tank off part way thru the re-install because I could see that the lock ring wasn’t secure. The second time, I carefully centered it so all three lock tabs were engaged - but it should have a larger diameter to not allow the ring to only engage 2 of the 3 tabs if not carefully centered.