Yeah, 20W50 or 10W40 should be fine for the cooler temps in CO. Also, there are concerns by many about the lower amount of ZDDP in modern oils made for cars with O2 sensors, and the effect it has on flat tappet cams such as the Triumph has. You can google that and have enough reading for a month or so. There are oils that have sufficient amounts of ZDDP, so probably best to search them out. I use 20W50 Valvoline VR1 Racing oil. There are ZDDP additives, but better to leave the oil chemistry to the pros. Your oil pressure values are normal. Since the oil pump is spinning at lower speeds at idle, less oil volume and pressure are produced. As RPMs increase, there's an oil pressure relief valve in the system that limits the pressures to between 60-70 PSI. It is adjustable, but yours is where it should be.