I installed an NV4500 in my '88 XJ--LOTS of fab work--you have to do significant cutting of the tunnel, which is a major part of the uni body, so major re-design is required to get the stiffness back. If I had it to do over again, I'd go the nv3500 route--decent low and overdrive, with tons less work to install. Also, the NV4500 is a real truck trans--slow shifting, stiff, not that much fun on the road, especially if you want to treat your XJ as a "sports car". I seldom use 1st because it's sow low (I'm running 4:56 and 33's), but 2nd is just a tad high to use as "1st". It's not much of a problem for me because I run a Chevy 350, so I've plenty of power.