Lower ball joint to Spindle bolts stuck

From looking at the install instructions.

It looks like Oldmanmopar has hit on the trouble.

The instructions say to use the origional bolt or bolt and nut from the 10 inch drum brakes. The bolt in question looks to be not an OEM bolt. I suspect the bolt is just press fit into the spindle.

The FSM shows bolts with nuts holding the lower ball joint to the spindle and the nuts face the drum.

You could try a the same technique to remove a tie rod end. Apply pressure to the bolt, and tap the side of the spindle where the nut goes through.

I know you tried heat but if you apply it localized to the spindle where the bolt goes through that can help too.

Push comes to shove. Drill out the bolt and go from there