Here is a very interesting article by a long time owner of a 1951 DeSoto 8 passenger sedan, and how he rebuilt a 265 flathead six for it. He tows a trailer at 70 MPH and reports that at 10000 feet altitude it runs as smooth as a turbine.
There is also some discussion of safe RPM's, temps, miles between overhauls etc.
The stock connecting rods are not weak as long as you respect the fact that you have a long stroke engine and keep the revs down to 3600 or so.
For trailer towing the stock cam will be fine. In fact a totally stock engine will handle the load with the least stress and the longest life.
