the motor going in is a 2003 5.3l lm7 engine so it fuel injected. i also have the ls1 fuel rails ill be using. it will use an10 lines up to the from the pump to the y block, an8 lines into the rails and to the regulator, then an an6 return after the regulator. the entire system is gunna be fuel hungry. also your right, the a1000 pump is not designed to pull. the manual pritty much says, the lower the better.
i think im gunna go with location A because i dont want to risk leaning out and damaging the engine. i was also think about using the fuel tank drain for the supply line. iv heard good and bad things about this set up but i htink it will work well.