I'd look for a 500-650CFM 4bbl w/vacuum secondaries. ANything larger tha that will bog the engine & flow more fuel than you can use. If you like to paly off-road I'd stay away from the Holley's because they need to either be upgraded w/the off-road float bowl kit (not cheap) or you need to spend the xtra $$$ on the Truck avanger carb wich already has the off-road float bowl kit & a few other upgrades. The Holleys are terrible in off-camber situations and need a LOT of tweeking to run well on a trail rig. If it's strictly a street truck you're probably fine with one. I prefer either the Motorcraft or Carter/Edelbrock carbs (Edelbrock just cut a licensing agreement w/Carter so Elelbrock carbs are just chromed Carters). IF you have deep pockets the Predator carbs are top of the line and you can vary the CFM rating with a set of changable cams. They aren't cheap but they DO offer excellent performance, although it's probably overkill on a street truck.