"...you almost never got an old one with a trigger pull that really needed any further 'enhancement' ".
Hmmm. Well, quite a few of us made some decent money doing "trigger jobs" on those guns whose pulls didn't need "ehnhancement." I think we often view the "good old days" with rose-colored glasses.
As to the barrel pinning, sorry, AKsRul.e. S&W made the cross cut in the barrel during barrel manufacture and before the barrel was installed. The frame hole was already drilled, also, so when the barrel was installed it was only a matter of driving in the pin. I know it is hard to believe, but precision manufacturing was being done many decades before CNC machines ever existed. In fact, guns don't even require much in the way of precision, compared to, say, a computer hard drive.