Planning is key.
Learn from my mistakes.
I converted my Pro-Flo to Holley's engine management system. Read about it here: http://www.edgesz28.com/edgesZ28/fuel.htm
If money is not an issue, avoid buying used and trying to piece together a DIY (Do-It-Yourself) system. Do yourself a big favor and learn from my mistakes, buy a complete Holley Stealth Ram or Commander Series single plan systems. Both are multi-point and use the same software.
When I originally bought the Pro-Flo, not having to use a laptop was one of my reasons for getting it. I eventually found that to be a handicap. The levels of tuning a Pro-Flo are limited and once you get it right, the weather changes and you have to do it again. The Pro-Flo is very temperature sensitive, especially on hot restart.
Get the Holley, you will not be disappointed. Both styles of systems have a manifold choice (standard 23* heads, or Vortec). They also come with different size injectors, depending on your setup and HP levels you will make.
Best of luck, Ed www.edgesz28.com