I have the same issue. Forum reading leads me to believe a connection is bad. The signal from the ignition/neutral safety switch isn't delivering the required current to turn the starter. There are mods that bypass that signal with a relay or...
Rising sun is legit, if they said that's the cost then that's the cost. There's also overland cruisers, but not going to be any cheaper. Lots of active members in the 406 cruisers clubhouse forum. They may have leads on another mechanic or a...
Bad ground somewhere. Some things are switched on the ground side in toyota. If my rear defroster is on ,I have wierd electrical issues. My dash lights will stay on with ignition off until I turn the defroster off.
I also have similar set up but with delta arms. Landtank double cardan quieted it down a little. My rear drive shaft was the real culprit. Take it apart and make sure the splines are greased well.