I found a good wiring harness and tilt column from an '89 waggy at the yard, then put it into my '74 J20. The swap went pretty well and now everything works except the brake lights.
Turn signal lights both work and so does the hazzard lights. tail lights, head lights - everything. The turn signal, headlights, etc wires all 'just worked' without having to modify anything. They all just plugged in, mostly because I also swaped in the steering column.
All the fuses are good and pass the continuity check on my multimeter.
I guess my question is this; how does the brake light system work? The switch is good and so is the fuse.
I've looked at the wiring diagrams here (but they don't have an '89 harness)
http://oljeep.com/gw/elec/GW_wiring.html