Here's some e-locker retrofits:
3rd gen into 4th:
http://www.toyota120.com/forum/showthread.php?t=20784
FJC'S into 4th:
http://www.toyota120.com/forum/showthread.php?t=22213
The first thread makes no mention of ratios. The second says that the FJ 3rd already came with a 3.73 ratio. Interesting.