[Richard]

Corey,

First thing I would try is to take a file and file two opposing flats on the exposed bolt. That will help the visegrips or pliers get a purchase on the bolt. I really think it is standard thread, righty tighty lefty loosey.

Second, if you can unbolt the OHLA and spin the assembly for access. Have someone with a portable welder come out and plug weld a nut on the bolt. The ground MUST be attached to the shaft. If the welder attaches the ground to anything other than the expose shaft the current will jump the bearings in the OHLA and ruin them. I have done this a bunch of times with bolts that are even broken below the surface. The heat usually breaks the bolt loose and it spins out by hand. Plug weld means place the nut over the bolt and weld inside the nut to bond the nut to the exposed bolt.