I just placed the torch on the head of the bolt, let it warm up cherry red then slowly cool, when around to all bolts doing this.
then gently try to loosen the bolt, if no go, then warm them up again, this time try drowning the bolts with cold water.
this event is a long distance race, not a short sprint.
sometimes it may take three or four times of heat/cool to break them loose.
I do not remember having any problems breaking the disc blade bolts loose, but I took my sweet time.
good luck and let me know how it works out.
I also have the owners manual for these plows.
its on the 8N ford tractor site.