What Drew said, plus - what you're using for a cam will guide what you need for a torque convertor. If your cam is fairly rowdy you'll probably need more convertor and should check with the torque convertor manufacturer for a recommendation. ATI is a quality company, and I've seen many people happy with Broader like Drew said too. The convertors usually come painted and I always sand the paint off the convertor hub where it goes into the crank because like Drew pointed out it's a tight fit.