Yeah you're going to have to post a TON more info. Like, what car, what engine, what radiator you're using (22", 26", number of rows), what pulley set up you have, what your alternator amperage is, how much horsepower you're making and how you plan on using the car.
Pullers are better because they don't obstruct air flow into the radiator when they're not running. But they can be limited for space. And then you're going to need at least 2,500 to 3000 CFM if it's going to be a stand alone electric fan. Typically OE fans are best, people have had a lot of luck with Ford Taurus or Contour fans (depending on radiator size). Chevy HHR and there's a Mercedes fan from a model I don't recall at the moment have been used on A-bodies as well.
There are also a TON of threads on this already to look to narrow your choices.