the 390 and the cj/boss toploaders are close ratio and the input is maybe 3/4 inch to short on the snout. if you have a big spline then the input can be extended and then you would have to get custom order clutch disc's. other than that, dan williams has a three peice input that can be used on big and small blocks and with close or wide ratio and can be had in small,big or 26 spline.