Being serious, whats going to net the most difference is a cam selected for your needs. I hear good things about the Summit K6900.
Never underestimate the power of a good tune either, get the timing set up tits; Then get in there with a standalone wideband, like an Innovate LC-2 from idle circuit all the way through WOT.. I picked up at least 50 ft/lbs and 50hp on tune alone, not to mention MPG. Cost me $170.