Don't believe the hype.
I've been running my 242 for 12 years, with various lift kits, and even an 8.8 in the last 4 years. I kept the stock driveshafts for all but 1 of them, and had little if any vibes (I believed the hype, and need a reason to spend money)
You should be just fine at 4.5" on your 89. Older models seem more resistant to vibes, as you will see. If you do get them, a simple TC drop will most likely alleviate it (see GoJeep's site to make your own)
TC Skids vary, but IIRC, most of them hang lower than the 231 because the case hangs down lower. I ran a Skid row without problems.
Hope this helps, and hope to see you on the trails!
John