hiya, nice car by the way, if you intend on keeping the car auto then you have 2 options,the bigger brother to what you have already fitted, the bw 65, or better still and fitted as standard to the last in the line rover sd1's the gm 180 th , this is a chevrolet built box and far better than the borg warner boxes in my opinion,and last but not least if you wanted to go manual people tend to go down the lt77 or tremec route!! hope this helps, tony