A tape measure is all you need. Measure the distance from the transfer case output to the front diff input and just keep that number in mind, and the tape in your hand, when you go to the junkyard. Measure the first one you find ('84 or '87, doesn't matter which) and you'll instantly have your answer. If the one you're measuring at the junkyard is short then you need the other one.
Or... Just buy one you know is too long, even if it's a couple feet longer, and have it cut, since you're going to have it worked on anyway.
NOTE: Due to the rising cost of ammunition, warning shots will no longer be given.
There's always a certain percentage of any population with the conviction that society is a conspiracy to deny them their rights.
The right to be totally ignorant of any useful knowledge seems to be the basic one. - Keith Laumer