Get a manual t-case that will mate to your transmission (be careful, you may have one of 2 or 3 different trannies that came with Rangers) then chop a hole in the transmission hump that will clear the shifter.
Cheaper to get a 4x4 computer from a wrecker... or diagnose the ailment and fix it.
check out therangerstation.com for fixes and tips.
I have an 88 electric shift Bronco II. On occassion it would not go into 4X4 and when released, would not pull the gears all the way out when cancelled (made a clunking sound). I found problems are in the wire connector at the transfer case. pull the plug and make sure the wire ends are clean, no corrosion and making good electrical connection. Use a small welding tip file and 220 grit sandpaper to clean, "fill" the area will white grease to keep out the moisture. It solved my problem.
Actually, Wren, I believe all the Ranger/BII 4x4 trannies have the same tranny to T-case flange pattern. All you should need to do is swap a manual T-case and shifter assembly. Also a good time to ditch the auto hubs if you don't already have manual hubs.
The most "difficult" part is if the output yokes are different (You may need to modify a socket to fit).
As for cost, a BW 1350 or BW1354 should be way less than a new ignition computer. Not to mention that if the T-case doesn't work, it will be a whole lot easier to get the wrecker to warrantee a T-case than any electronic component...
If you are lucky, it may even be just the shift motor itself that is on the way out (although if it IS just the shift motor, I'd still replace it with a manual T-case...for future reliability)
Something to watch out for....Replacing my Tcase I found out The tranfer case mount bolt threading changes. some are imperial and some are the near equivalent in metric.
...Shameless plug...If your going to do it.. I ve got the stock front end stuff still i.e. manual hubs and D28 washers spacers, locknuts etc