Gerry:
Triangle made some fine kits for the time and place (and many are now offered by Weisman). They can build into excellent models, and welcome the addition of some modern, time saving details as you suggest. I frequently substitute new trucks, coupler cut levers, and a one-piece brake shot, if a suitable one is available. Also, be aware that many will require the addition of Kadee #4 couplers, which are no longer in production.
Weigh all the parts before you start and add some weight to bring the car up to operating weight. I add some lead solder on the underside of flat cars and gons between the sills. Also, the steel underframe cars (SUF) use a couple pieces of brass channel for the center beam, which requires soldering and some filing. Time and care will produce a great result.
I also have a TSM/Weisman RGS Plow Flanger 02 in the cabinet slated for construction in the future. Mr. Mark Evans is the expert. You are wise to consult him.
Keith Hayes
Leadville in Sn3