The nut it torqued to 380 ft-lbs, sits for years, and is subject to heat from
the brakes.  The solution is to get a cut-off tool, grinder, chisel, Dremel,
etc, and cut the nut off.  Don't waste time trying to turn it.  Just go to
the dealer or Bus Depot or whatever and spend the few bucks for some new
nuts.  Be careful of the threads when you do cut it off.
     When you torque the new ones on, remember that a 190 lb man standing on
the end of a 2 ft. piece of pipe on a breaker bar gives you 380 ft-lbs.  That
works for me.

best of luck

Bill Marshall
85 GL Tiico w/ new drums and brakes
Phoenix AZ