The 231 I have measures in right around 17", give or take an 1/8th" or so, from the trans mating surface to the end of the output shaft. As far as driveshaft issues go, there really weren't any....but remember, mine started as a 2WD originally. I picked up a spare XJ rear DS somewhere along the way (but I have no idea what it came out of) that just magically seemed to match the measurements I made once I slapped all the 4WD stuff in. I got the measurement on advice from the guy who will be cutting my 2WD MJ shaft down. He said to bury the slip yoke into the TC and back it out 1", then measure the distance from the center of the yoke U-joint cap the the center of the pinoin yoke u-joint cap...which I measured out to be 47.5". The XJ shaft I had was 48", so I threw it up in there and all seems to be working well with the stock configuration I have. I did have to use an XJ slip-yoke (like the spare one you sent me) because of the difference in the spline count on the 2WD MJ yoke, and the XJ yoke is a tad shorter than the MJ yoke (about 3/8" or so). I've also seen posts that say YJ yokes are a bit longer than XJ yokes, I think...maybe you could make up the length difference by using a different yoke???
