Re: 89 full size 4x4 issue
First thing is to verify that your 4x4 is working. If possible, put a mark on your front drive shaft, drive the vehicle in 4wheel, then inspect to verify rotation of the front drive shaft.
If it is indeed the locking hubs then, there are a few things you could try. First off, i'll just say that this could be due to improper lubrication of the hubs, which may now have frozen. The best practice would be to dissasemble the hubs, and lubricate with first ATF to clean, then get the special low viscosity grease for auto hubs (from ford if possible).
With out wanting to do all of that, you could try simply driving the vehicle for several miles at low speed to hopefully warm up and loosen the front hubs. beware though as you don't want them to engage while at higher speeds.
Or you could try jacking up the front end and rotating the front drive shaft by hand while having a friend lightly tap on the front hubs with a rubber mallet to try to loosen and engage the hubs.
Remember, it could be that only one hub is not engaging and the front differential with no limited slip is directing all of the power to that wheel (i.e. the wheel with least traction).
Short of all of this, you may have to go out and buy new hubs. just get manual ones since they are cheap and easy to find at the parts store. You will need a special socket to remove the bearing retaining nuts (something like 2 3/8", i forget the exact size, but it will be labeled as used for ford full size hubs).
If you attempt to remove the hub yourself, be sure to extract the hub nut retaining pin before loosening the bearing retaining nut, otherwise you could damage the assembly. you will need a magnet or pick set to remove this small pin which is slid into the spindle to stop the retaining nut from loosening.