I am 5’7”, 160lbs with a 39” chest. I have a size 40 and wish I had a 38.
We are pretty much the same size except I am 1" taller. The 40 vs 38 reminded me that when I tried on a 40 Mulholland while in Japan this past winter, I am now recalling the 40 was not snug or really fitted and if they had a 38 I would have tried it to compare. The 40 did feel OK and not overly big or roomy but unfortunately there was no 38 on hand to compare with.