There are two versions - actually three but the Overdrive unit is basicially a gear swap internally to the transmission. The major difference are 18 spline input shaft for most big blocks and the 23 spline for the rest. Iron cased - heavy (insert cuss word here) to lift whil on your back. The easist way that I have filled is just to the bottom of the drain plug. I want to say around 2 1/2 quarts.