Joseph Smith read from James. It is likely that Joseph Smith did not just open to James, but read the Pauline episodes first. Joseph Smith would have been reading over the doctrines of the old church while visiting and investigating the churches in his area at his time.

I believe that Joseph Smith had a personal and deep relationship with Paul. Their lives are parallel. Converted through seeing the Lord, chosen to be a great church leader in building the Church, persecuted, imprisoned, and martyred. It is interesting how the only physical description of Paul comes from Joseph Smith.