I went through this a couple times with my 164 in Panama (where it is wet most of the time)
and in my estimation it is not good to heat the threaded end of the bolt unless you are sure
you are going to replace it. What I did was to heat the tube through which the bolt goes
and that will loosen the rust between the bolt and the tube. I found that when the tube
was really hot the bolt could be turned and driven endwise. I also found that the threads
on one end of the center rod were the same as on the bolt and I was able to screw a piece
of an old one onto the bolt and use that to drive the bolt a little way endwise.
Once you have driven it as far endwise as you can that way, a brass drift is good with a
hammer of at least 3#.

After you get it out, before you put it back in make sure it is STRAIGHT (mine was slightly bent) and grease both the bolt and the inside of tube WELL to keep out further moisture.
--
George Downs Bartlesville, Oklahoma