I have 3 different bell housings that have a different size hole for each one of them. for the newer trannys you will need the aluminum bell housing as for the older 3-4 speeds they all have specific bell housings. the aluminum housing you will need the cross member that bolts to the frame and mounts the tranny in the middle with the 2 bolts, the older trannys have the cross member in place as it is rivited to the frame and requires a tranny with "dog ears" that bolt to the tranny, an even older tranny uses bolts that mount in the middle of the bell housing on the bottom of it. my suggetion is to do an out of vehicle mock up first to see if it is all compatible before installation.........