It'll take a little finesse, but can be done. How easily depends on your tool collection. Have done a couple ways with good results. @Troy is right about switching to new style (when there's no gen.1 ash bucket involved). Would still try to salvage for a future project that has the gen.1 bucket.
Method #1: Cool a can of penetrating oil in the fridge. Use a propane torch to directly heat the rod, not the nut. Then spray the rod w/ cold penetrating oil. The rapid cool should break the rust bond.
Method #2: Use an open end wrench to brace the nut. Then hammer lightly against end of rod (air chisel with hammer bit would be preferable).
Method #3: Cut the rod flush on both sides of nut. Remove & disassemble blades/nut. Secure nut and drill rod out of it. Rod will be about an inch shorter when re-installed.
Method #4: Haven't had opportunity to try yet, but in theory, it should work. Grind down the fixed end of a C-clamp into a forked end. Put forked end around rod & crank it.