Leave the '87 driveshaft, you don't need it, (unless it's free, then I'd take it and throw it in my spare parts bin) but your current driveshaft will hook up fine to the '87 44. I swapped an '87 44 into my '94, (which originally had an 8.25) and it was a perfect fit. No problems at all. Just make sure your gears match up. I believe all XJ 44's came with 3,73 gears, which is what your front should be as long as you have a 6 cylinder.