I think it may be time to consider replacing the inner cowl panel if you don't want to replace the pillar post. Short of that even if you get the bolts out the nuts are turning and useless. And with 5/6 junk you will never get a top quality repair without some surgery. What condition are your inner and outer cowls? If you have to replace them (most are rust prone or holed on original trucks) now may be the time to plan for it if they are coming off you can stop the temporary measures.
