I’ve never seen a pope mower but it’s possible that what you’re attempting to disassemble may have been together a very long time.
If the penetrant won’t loosen it then I’d try heat. I’ve had shafts semi fuse onto bearings and various bushings partially migrate into alloy in things I’ve tried to fix, so sometimes nothing works but cycling things with heat can really help to loosen things up.
This is what I do with old bits of cars and machinery.
If the bolt part is externally threaded (like a standard bolt) then I put the whole assembly in a thick plastic bag in a freezer overnight along with whatever spanner I am going to use to try to turn the bolt. This will reduce the amount of warming of the bolt that will occur just by working on it.
The next day sort out a good solid way to hold the assembly. I have a blacksmith’s vice and often use that as I can heat it up til it’s nice and hot without damage, however you can also use a big pair of vice grips. I apply my map torch (it’s easy to control heat) selectively to the outside while using the frozen spanner on the bolt. I apply very slight force in the tightening direction until I feel just hint of movement before then loosening.
If the part you can grab with a tool is internally threaded then you’ll need to heat that tool and and cool what you’re using to hold the assembly instead.
If you perform repeated cycles of heating and cooling with judicious amounts of force applied that can give a result. It’s a game of patience. If it doesn’t move I try another setup and another cycle of heat and cold.
With fuel systems there are residues that act like both salts and adhesives. We had a carb cleaner that came in a bucket and you’d give the component a good external clean with the parts washer and degreaser then soak the whole assembly in the bucket, strip it back as far as you could and put it back in the bucket. It was very effective at both cleaning and loosening parts. I don't know what was in it but you had to wear special gloves and none of it was allowed into a sink or drain. It was a long lasting product that would do a number of carbys or throttle bodies before losing its effectiveness.
