Both the AFP and Precision systems are quality units. Both will fit either vertical or horizontal sumps. With the Precision system, you will still need to have nipples, fittings and fuel lines on hand.
One thing that I think is important is that Don is only a phone call away, and very receptive to helping. Sometimes at Precision it's hard to get ahold of the right people when a situation or questions arise.
Shameless plug here, Airflow has a fuel systems seminar once or twice a year. It is very informative and worth going to. Their next seminar I am told is the first weekend of Nov. Call Don or Colleen for more information.