Landcruiser sporadically wont start when hot

I have a 91 Landcruiser. Ran it for a while with no problems. I have had it towed about 7 times in the past 8 months. I stopped running it because of this. ONce it gets hot, it wont start. It will just click like a bad starter. Well, we have had the starter replaced, several fuses replaced, redid most of the wiring, replaced battery cables and we are still having the intermittent problem of starting when it is hot (even if the LC hasnt been started yet and the outside temp is over 100 degrees, it sometimes has problems starting). We have been to two different mechanic shops and one of them basically gave up, said there was nothing they could do about it, because they only experienced the problem with it once and couldnt do it again. The other shop kept it for several days and ran several diagnostics, hence replacing fuses, wiring, cables, etc and then the LC ran fine for about 1 month, and then started having probs again. I have since parked the LC and am running a difference truck now for the LC is so unreliable, and I have a 75 mile one way commute. We use the LC occassionally on the weekends to keep it from just sitting, but we only take it places where we dont have to shut it off, someone can stay in the vehicle, while the other person runs into the store really quick. Does anyone have any ideas?? We cannot figure out what is wrong with this and I would really like to get it reliable so we can do the off roading we wanted to do with it.