I had a discussion with Dr. Richard Carrier about dating the Pauline Epistles to the first century. Here is what he had to say.
Paul wrote before the Jewish War, which began in 66, and probably before the Neronian persecution of 64 (if such there was), as neither are ever mentioned in his letters (yet both, and their consequences, would have been too huge not to affect anything he said, esp. in Romans); and he wrote well after Aretas assumed control of Damascus (which he mentions in 2 Corinthians 11:32), which was between the years of 37 and 40; and most (if not all) of his literary activity came 14 to 17 years after his conversion (Galatians 1:15-18, 2:1; possibly also 2 Corinthians 12:2); all of which argues for his letters being written in the 50s.
For a detailed analysis: Gerd Lüdemann, Paul, The Founder of Christianity (2002), which also details why we should trust a chronology derived only from Paul’s letters and not from Acts.
One can avoid this conclusion only by assuming these are all lies and the letters are fabricated to look like they were written in the 50s. That’s an enormous ad hoc assumption, which has no inherent probability (even out of the gate, much less after considering how little the forgers even bothered to polemicize against the Gospel version of Jesus etc., or do or say anything distinctive of the second century or even intelligible in that context–as opposed to, for example, the Pastorals).