If you can chase down like a 1994 XLT RMK suspension you can put that in the '89 pretty easy and pick up the "xtra 10" type travel. In those years they went to the CRC front end which was unequal length radius rods... that suspension won't work on the front because of the bulkhead differences.
Also, if you can find the standard long travel suspension you need to look closely at where the steering rods come out of the bulkhead. On your 89 that opening is going to be pretty small compared to the 94 for example. All you need to do is cut the bottom of the opening bigger, down towards the bottom of the bellypan, to allow for the steering rod to travel the full distance. If you don't, when you unload the suspension (jump it), the steering rod will hit the bulkhead and eventually snap.
sled_guy
